Apple

PlatformSecurity

May 2022

2Apple Platform Security

Contents

Apple platform security 5

Introduction to Apple platform security 5

Hardware security and biometrics 7

Hardware security overview 7

Apple SoC security 8

Secure Enclave 9

FaceID and TouchID 18

Hardware microphone disconnect 26

Express Cards with power reserve 27

System security 28

System security overview 28

Secure boot 28

Signed system volume security in iOS, iPadOS andmacOS 51

Secure software updates 53

Operating system integrity 55

Additional macOS system security capabilities 57

System security for watchOS 68

Random number generation 71

Apple Security Research Device 72

Encryption and Data Protection 74

Encryption and Data Protection overview 74

Passcodes and passwords 74

Data Protection 77

FileVault 89

How Apple protects users’ personal data 92

Digital signing and encryption 95

3Apple Platform Security

App security 97

App security overview 97

App security in iOS and iPadOS 98

App security in macOS 103

Secure features in the Notes app 108

Secure features in the Shortcuts app 109

Services security 110

Services security overview 110

AppleID and Managed AppleID 110

iCloud 112

Passcode and password management 121

ApplePay 130

Using Apple Wallet 144

iMessage 154

Secure Apple Messages for Business 157

FaceTime security 157

Find My 158

Continuity 161

Network security 165

Network security overview 165

TLS security 165

IPv6 security 166

Virtual private network (VPN) security 167

Wi-Fi security 168

Bluetooth security 172

Ultra Wideband security in iOS 173

Single sign-on 173

AirDrop security 174

Wi-Fi password sharing security on iPhone andiPad 176

Firewall security in macOS 176

Developer kit security 177

Developer kit security overview 177

HomeKit security 177

SiriKit security for iOS, iPadOS and watchOS 182

DriverKit security for macOS 183

ReplayKit security in iOS and iPadOS 183

ARKit security in iOS and iPadOS 185

4Apple Platform Security

Secure device management 186

Secure device management overview 186

Pairing model security for iPhone and iPad 186

Mobile device management 187

Apple Configurator security 195

Screen Time security 196

Glossary 198

Document revision history 203

5Apple Platform Security

Apple platform security

Introduction to Apple platform security

Apple designs security into the core of its platforms. Building on the experience of creating

one of the world’s most advanced mobile operating systems, Apple has created security

architectures that address the unique requirements of mobile, watch, desktop and home.

Every Apple device combines hardware, software and services designed to work together

for maximum security and a transparent user experience in service of the ultimate goal

of keeping personal information safe. For example, Apple-designed silicon and security

hardware powers critical security features. And software protections work to keep the

operating system and third-party apps protected. Finally, services provide a mechanism

for secure and timely software updates, power a protected app ecosystem, and facilitate

secure communications and payments. As a result, Apple devices protect not only the

device and its data but the entire ecosystem, including everything users do locally, on

networks and with key internet services.

Just as we design our products to be simple, intuitive and capable, we design them to

be secure. Key security features, such as hardware-based device encryption, can’t be

disabled by mistake. Other features, such as FaceID and TouchID, enhance the user

experience by making it simpler and more intuitive to secure the device. And because many

of these features are enabled by default, users or IT departments don’t need to perform

extensive configurations.

This documentation provides details about how security technology and features are

implemented within Apple platforms. It also helps organisations combine Apple platform

security technology and features with their own policies and procedures to meet their

specific security needs.

The content is organised into the following topic areas:

• Hardware security and biometrics: The silicon and hardware that forms the

foundation for security on Apple devices, including Apple silicon, the Secure Enclave,

cryptographic engines, FaceID and TouchID

• System security: The integrated hardware and software functions that provide for the

safe boot, update and ongoing operation of Apple operating systems

• Encryption and Data Protection: The architecture and design that protects user data

if the device is lost or stolen or if an unauthorised person or process attempts to use or

modify it

• App security: The software and services that provide a safe app ecosystem and enable

apps to run securely and without compromising platform integrity

6Apple Platform Security

• Services security: Apple’s services for identification, password management,

payments, communications and finding lost devices

• Network security: Industry-standard networking protocols that provide secure

authentication and encryption of data in transmission

• Developer kit security: Framework “kits” for secure and private management of home and

health, as well as extension of Apple device and service capabilities to third-party apps

• Secure device management: Methods that allow management of Apple devices, help

prevent unauthorised use and enable remote wipe if a device is lost or stolen

A commitment to security

Apple is committed to helping protect customers with leading privacy and security

technologies — designed to safeguard personal information — and comprehensive

methods, to help protect corporate data in an enterprise environment. Apple rewards

researchers for the work they do to uncover vulnerabilities by offering the Apple

Security Bounty. Details of the programme and bounty categories are available at

https://developer.apple.com/security-bounty/.

We maintain a dedicated security team to support all Apple products. The team provides

security auditing and testing for products, both under development and released. The

Apple team also provides security tools and training and actively monitors for threats and

reports of new security issues. Apple is a member of the Forum of Incident Response and

Security Teams (FIRST).

Apple continues to push the boundaries of what’s possible in security and privacy. It uses

custom silicon across its product lineup — from AppleWatch to iPhone and iPad, to the

T2 Security Chip and Apple silicon in Mac — powering not only efficient computation but

also security. For example, Apple silicon forms the foundation for secure boot, FaceID

and TouchID, and Data Protection. In addition, security features on devices powered by

Apple silicon — such as Kernel Integrity Protection, Pointer Authentication Codes and Fast

Permission Restrictions — help thwart common types of cyberattack. Therefore, even if

attacker code somehow executes, the damage it can do is dramatically reduced.

To make the most of the extensive security features built into our platforms, organisations

are encouraged to review their IT and security policies to ensure that they are taking full

advantage of the layers of security technology offered by these platforms.

To learn more about reporting issues to Apple and subscribing to security notifications,

seeReport a security or privacy vulnerability.

Apple believes privacy is a fundamental human right and has numerous built-in controls

and options that allow users to decide how and when apps use their information,

as well as what information is being used. To learn more about Apple’s approach

to privacy, privacy controls on Apple devices and the Apple privacy policy, see

https://www.apple.com/uk/privacy.

Note: Unless otherwise noted, this documentation covers the following operating system

versions: iOS 15.4, iPadOS 15.4, macOS 12.3, tvOS 15.4 and watchOS 8.5.

7Apple Platform Security

Hardware security and biometrics

Hardware security overview

For software to be secure, it must rest on hardware that has security built in. That’s

why Apple devices — using iOS, iPadOS, macOS, tvOS and watchOS — have security

capabilities designed into silicon. These capabilities include a CPU that powers system

security features as well as additional silicon that’s dedicated to security functions.

Security-focused hardware follows the principle of supporting limited and discretely

defined functions in order to minimise attack surface. Such components include a Boot

ROM, which forms a hardware root of trust for secure boot, dedicated AES engines

for efficient and secure encryption and decryption, and a Secure Enclave. The Secure

Enclave is a system on chip (SoC) that is included on all recent iPhone, iPad, AppleWatch,

AppleTV and HomePod devices, and on a Mac with Apple silicon as well as those with the

Apple T2 Security Chip. The Secure Enclave itself follows the same principle of design as

the SoC does, containing its own discrete Boot ROM and AES engine. The Secure Enclave

also provides the foundation for the secure generation and storage of the keys necessary

for encrypting data at rest, and it protects and evaluates the biometric data for FaceID and

TouchID.

Storage encryption must be fast and efficient. At the same time, it can’t expose the data

(or keying material) it uses to establish cryptographic keying relationships. The AES

hardware engine solves this problem by performing fast inline encryption and decryption

as files are written or read. A special channel from the Secure Enclave provides necessary

keying material to the AES engine without exposing this information to the Application

Processor (or CPU) or overall operating system. This helps ensure that the Apple Data

Protection and FileVault technologies protect users’ files without exposing long-lived

encryption keys.

Apple has designed secure boot to protect the lowest levels of software against tampering

and to allow only trusted operating system software from Apple to load at startup. Secure

boot begins in immutable code called the Boot ROM, which is laid down during Apple SoC

fabrication and is known as the hardware root of trust. On Mac computers with a T2 chip,

trust for macOS secure boot begins with the T2. (Both the T2 chip and the Secure Enclave

also execute their own secure boot processes using their own separate Boot ROM — this is

an exact analogue to how the A-series and M1 family of chips boot securely.)

The Secure Enclave also processes face and fingerprint data from FaceID and TouchID

sensors in Apple devices. This provides secure authentication while keeping user biometric

data private and secure. It also allows users to benefit from the security of longer and

more complex passcodes and passwords with, in many situations, the convenience of swift

authentication for access or purchases.

8Apple Platform Security

Apple SoC security

Apple-designed silicon forms a common architecture across all Apple products and now

powers Mac as well as iPhone, iPad, AppleTV and AppleWatch. For over a decade, Apple’s

world-class silicon design team has been building and refining Apple systems on chip

(SoCs). The result is a scalable architecture designed for all devices that leads the industry

in security capabilities. This common foundation for security features is only possible from

a company that designs its own silicon to work with its software.

Apple silicon has been designed and fabricated to specifically enable the system security

features detailed below.

Feature A10 A11, S3 A12, S4 A13, S5 A14, A15,

S6, S7

M1 Family

Kernel

Integrity

Protection

Fast

Permission

Restrictions



System

Coprocessor

Integrity

Protection

 

Pointer

Authentication

Codes

 

Page

Protection

Layer

See Note

below.

Note: Page Protection Layer (PPL) requires that the platform execute only signed and

trusted code; this is a security model that isn’t applicable in macOS.

Apple-designed silicon also specifically enables the Data Protection capabilities detailed

below.

Feature A10 A11, S3 A12, S4 A13, S5 A14, A15, S6, S7,

M1 Family

Sealed Key

Protection (SKP)

recovery OS — All

Data Protection

Classes

protected

Alternative

boots of DFU,

Diagnostics and

Update — Class

A, B and C data

protected

 

9Apple Platform Security

Secure Enclave

The Secure Enclave is a dedicated secure subsystem in the latest versions of iPhone, iPad,

iPodtouch, Mac, AppleTV, AppleWatch and HomePod.

Overview

The Secure Enclave is a dedicated secure subsystem integrated into Apple systems on chip

(SoCs). The Secure Enclave is isolated from the main processor to provide an extra layer

of security and is designed to keep sensitive user data secure even when the Application

Processor kernel becomes compromised. It follows the same design principles as the

SoC— a Boot ROM to establish a hardware root of trust, an AES engine for efficient and

secure cryptographic operations, and protected memory. Although the Secure Enclave

doesn’t include storage, it has a mechanism to store information securely on attached

storage separate from the NAND flash storage that’s used by the Application Processor

and operating system.

10Apple Platform Security

The Secure Enclave is a hardware feature of most versions of iPhone, iPad, Mac, AppleTV,

AppleWatch and HomePod — namely:

• iPhone 5s or later

• iPad Air or later

• MacBook Pro computers with Touch Bar (2016 and 2017) that contain the Apple T1 Chip

• Intel-based Mac computers that contain the Apple T2 Security Chip

• Mac computers with Apple silicon

• AppleTV HD or later

• AppleWatch Series 1 or later

• HomePod and HomePod mini

Secure Enclave Processor

The Secure Enclave Processor provides the main computing power for the Secure Enclave.

To provide the strongest isolation, the Secure Enclave Processor is dedicated solely for

Secure Enclave use. This helps prevent side-channel attacks that depend on malicious

software sharing the same execution core as the target software under attack.

The Secure Enclave Processor runs an Apple-customised version of the L4 microkernel. It’s

designed to operate efficiently at a lower clock speed that helps protect it against clock

and power attacks. The Secure Enclave Processor, starting with the A11 and S4, includes

a memory-protected engine and encrypted memory with anti-replay capabilities, secure

boot, a dedicated random number generator and its own AES engine.

Memory Protection Engine

The Secure Enclave operates from a dedicated region of the device’s DRAM memory.

Multiple layers of protection isolate the Secure Enclave protected memory from the

Application Processor.

When the device starts up, the Secure Enclave Boot ROM generates a random ephemeral

memory protection key for the Memory Protection Engine. Whenever the Secure Enclave

writes to its dedicated memory region, the Memory Protection Engine encrypts the block

of memory using AES in Mac XEX (xor-encrypt-xor) mode, and calculates a Cipher-

based Message Authentication Code (CMAC) authentication tag for the memory. The

Memory Protection Engine stores the authentication tag alongside the encrypted memory.

When the Secure Enclave reads the memory, the Memory Protection Engine verifies the

authentication tag. If the authentication tag matches, the Memory Protection Engine

decrypts the block of memory. If the tag doesn’t match, the Memory Protection Engine

signals an error to the Secure Enclave. After a memory authentication error, the Secure

Enclave stops accepting requests until the system is rebooted.

11Apple Platform Security

Starting with the Apple A11 and S4 SoCs, the Memory Protection Engine adds replay

protection for Secure Enclave memory. To help prevent replay of security-critical data, the

Memory Protection Engine stores a unique one-off number, called a nonce, for the block

of memory alongside the authentication tag. The nonce is used as an additional tweak for

the CMAC authentication tag. The nonces for all memory blocks are protected using an

integrity tree rooted in dedicated SRAM within the Secure Enclave. For writes, the Memory

Protection Engine updates the nonce and each level of the integrity tree up to the SRAM.

For reads, the Memory Protection Engine verifies the nonce and each level of the integrity

tree up to the SRAM. Nonce mismatches are handled similarly to authentication tag

mismatches.

On Apple A14, A15, the M1 family and later SoCs, the Memory Protection Engine supports

two ephemeral memory protection keys. The first is used for data private to the Secure

Enclave and the second is used for data shared with the Secure Neural Engine.

The Memory Protection Engine operates inline and transparently to the Secure Enclave.

The Secure Enclave reads and writes memory as if it were regular unencrypted

DRAM, whereas an observer outside the Secure Enclave sees only the encrypted and

authenticated version of the memory. The result is strong memory protection without

performance or software complexity tradeoffs.

Secure Enclave Boot ROM

The Secure Enclave includes a dedicated Secure Enclave Boot ROM. Like the Application

Processor Boot ROM, the Secure Enclave Boot ROM is immutable code that establishes the

hardware root of trust for the Secure Enclave.

On system startup, iBoot assigns a dedicated region of memory to the Secure Enclave.

Before using the memory, the Secure Enclave Boot ROM initialises the Memory Protection

Engine to provide cryptographic protection of the Secure Enclave protected memory.

The Application Processor then sends the sepOS image to the Secure Enclave Boot ROM.

After copying the sepOS image into the Secure Enclave protected memory, the Secure

Enclave Boot ROM checks the cryptographic hash and signature of the image to verify that

the sepOS is authorised to run on the device. If the sepOS image is properly signed to run

on the device, the Secure Enclave Boot ROM transfers control to sepOS. If the signature

isn’t valid, the Secure Enclave Boot ROM is designed to prevent any further use of the

Secure Enclave until the next chip reset.

On Apple A10 and later SoCs, the Secure Enclave Boot ROM locks a hash of the sepOS

into a register dedicated to this purpose. The Public Key Accelerator uses this hash for

operating-system-bound (OS-bound) keys.

12Apple Platform Security

Secure Enclave Boot Monitor

On Apple A13 and later SoCs, the Secure Enclave includes a Boot Monitor designed to

ensure stronger integrity on the hash of the booted sepOS.

At system startup, the Secure Enclave Processor’s System Coprocessor Integrity

Protection (SCIP) configuration helps prevent the Secure Enclave Processor from executing

any code other than the Secure Enclave Boot ROM. The Boot Monitor helps prevent the

Secure Enclave from modifying the SCIP configuration directly. To make the loaded sepOS

executable, the Secure Enclave Boot ROM sends the Boot Monitor a request with the

address and size of the loaded sepOS. On receipt of the request, the Boot Monitor resets

the Secure Enclave Processor, hashes the loaded sepOS, updates the SCIP settings to

allow execution of the loaded sepOS and starts execution within the newly loaded code.

As the system continues booting, this same process is used whenever new code is made

executable. Each time, the Boot Monitor updates a running hash of the boot process. The

Boot Monitor also includes critical security parameters in the running hash.

When boot completes, the Boot Monitor finalises the running hash and sends it to the

Public Key Accelerator to use for OS-bound keys. This process is designed so that

operating system key binding can’t be bypassed even with a vulnerability in the Secure

Enclave Boot ROM.

True Random Number Generator

The True Random Number Generator (TRNG) is used to generate secure random data. The

Secure Enclave uses the TRNG whenever it generates a random cryptographic key, random

key seed or other entropy. The TRNG is based on multiple ring oscillators post-processed

with CTR_DRBG (an algorithm based on block ciphers in Counter Mode).

Root Cryptographic Keys

The Secure Enclave includes a unique ID (UID) root cryptographic key. The UID is unique to

each individual device and isn’t related to any other identifier on the device.

A randomly generated UID is fused into the SoC at manufacturing time. Starting with A9

SoCs, the UID is generated by the Secure Enclave TRNG during manufacturing and written

to the fuses using a software process that runs entirely in the Secure Enclave. This process

protects the UID from being visible outside the device during manufacturing and therefore

isn’t available for access or storage by Apple or any of its suppliers.

sepOS uses the UID to protect device-specific secrets. The UID allows data to be

cryptographically tied to a particular device. For example, the key hierarchy protecting the

file system includes the UID, so if the internal SSD storage is physically moved from one

device to another, the files are inaccessible. Other protected device-specific secrets include

FaceID or TouchID data. On a Mac, only fully internal storage linked to the AES engine

receives this level of encryption. For example, neither external storage devices connected

over USB nor PCIe-based storage added to the 2019 Mac Pro are encrypted in this fashion.

The Secure Enclave also has a device group ID (GID), which is common to all devices that

use a given SoC (for example, all devices using the Apple A15 SoC share the same GID).

The UID and GID aren’t available through Joint Test Action Group (JTAG) or other

debugging interfaces.

13Apple Platform Security

Secure Enclave AES Engine

The Secure Enclave AES Engine is a hardware block used to perform symmetric

cryptography based on the AES cipher. The AES Engine is designed to resist leaking

information by using timing and Static Power Analysis (SPA). Starting with the A9 SoC, the

AES Engine also includes Dynamic Power Analysis (DPA) countermeasures.

The AES Engine supports hardware and software keys. Hardware keys are derived from

the Secure Enclave UID or GID. These keys stay within the AES Engine and aren’t made

visible even to sepOS software. Although software can request encryption and decryption

operations with hardware keys, it can’t extract the keys.

On Apple A10 and newer SoCs, the AES Engine includes lockable seed bits that diversify

keys derived from the UID or GID. This allows data access to be conditioned on the

device’s mode of operation. For example, lockable seed bits are used to deny access to

password-protected data when booting from Device Firmware Update (DFU) mode. For

more information, see Passcodes and passwords.

AES Engine

Every Apple device with a Secure Enclave also has a dedicated AES256 crypto engine

(the“AES Engine”) built into the direct memory access (DMA) path between the NAND

(non-volatile) flash storage and main system memory, making file encryption highly efficient.

On A9 or later A-series processors, the flash storage subsystem is on an isolated bus that’s

granted access only to memory containing user data through the DMA crypto engine.

At boot time, sepOS generates an ephemeral wrapping key using the TRNG. The Secure

Enclave transmits this key to the AES Engine using dedicated wires designed to prevent it

from being accessed by any software outside the Secure Enclave. sepOS can then use the

ephemeral wrapping key to wrap file keys for use by the Application Processor file-system

driver. When the file-system driver reads or writes a file, it sends the wrapped key to the

AES Engine, which unwraps the key. The AES Engine never exposes the unwrapped key to

software.

Note: The AES Engine is a separate component to both the Secure Enclave and the Secure

Enclave AES Engine, but its operation is closely tied to the Secure Enclave, as shown below.

14Apple Platform Security

Public Key Accelerator

The Public Key Accelerator (PKA) is a hardware block used to perform asymmetric

cryptography operations. The PKA supports RSA and ECC (Elliptic Curve Cryptography)

signing and encryption algorithms. The PKA is designed to resist leaking information using

timing and side-channel attacks such as SPA and DPA.

The PKA supports software and hardware keys. Hardware keys are derived from the Secure

Enclave UID or GID. These keys stay within the PKA and aren’t made visible even to sepOS

software.

Starting with A13 SoCs, the PKA’s encryption implementations have been proved to be

mathematically correct using formal verification techniques.

On Apple A10 and later SoCs, the PKA supports OS-bound keys, also referred to as

SealedKey Protection (SKP). These keys are generated using a combination of the device’s

UID and the hash of the sepOS in use on the device. The hash is provided by the Secure

Enclave Boot ROM, or by the Secure Enclave Boot Monitor on Apple A13 and later SoCs.

These keys are also used to verify the sepOS version when making requests to certain

Apple services and are also used to improve the security of passcode-protected data by

helping to prevent access to keying material if critical changes are made to the system

without user authorisation.

Secure non-volatile storage

The Secure Enclave is equipped with a dedicated secure non-volatile storage device. The

secure non-volatile storage is connected to the Secure Enclave using a dedicated I2C bus,

so it can only be accessed by the Secure Enclave. All user data encryption keys are rooted

in entropy stored in the Secure Enclave non-volatile storage.

In devices with A12, S4 and later SoCs, the Secure Enclave is paired with a Secure

Storage Component for entropy storage. The Secure Storage Component is itself

designed with immutable ROM code, a hardware random number generator, a per-device

unique cryptographic key, cryptography engines and physical tamper detection. The

Secure Enclave and Secure Storage Component communicate using an encrypted and

authenticated protocol that provides exclusive access to the entropy.

Devices first released in autumn 2020 or later are equipped with a 2nd-generation Secure

Storage Component. The 2nd-generation Secure Storage Component adds counter

lockboxes. Each counter lockbox stores a 128-bit salt, a 128-bit passcode verifier, an 8-bit

counter and an 8-bit maximum attempt value. Access to the counter lockboxes is through

an encrypted and authenticated protocol.

Counter lockboxes hold the entropy needed to unlock passcode-protected user data. To

access the user data, the paired Secure Enclave must derive the correct passcode entropy

value from the user’s passcode and the Secure Enclave’s UID. The user’s passcode can’t

be learned using unlock attempts sent from a source other than the paired Secure Enclave.

If the passcode attempt limit is exceeded (for example, 10 attempts on iPhone), the

passcode-protected data is erased completely by the Secure Storage Component.

15Apple Platform Security

To create a counter lockbox, the Secure Enclave sends the Secure Storage Component the

passcode entropy value and the maximum attempt value. The Secure Storage Component

generates the salt value using its random number generator. It then derives a passcode

verifier value and a lockbox entropy value from the provided passcode entropy, the Secure

Storage Component’s unique cryptographic key and the salt value. The Secure Storage

Component initialises the counter lockbox with a count of 0, the provided maximum

attempt value, the derived passcode verifier value and the salt value. The Secure Storage

Component then returns the generated lockbox entropy value to the Secure Enclave.

To retrieve the lockbox entropy value from a counter lockbox later, the Secure Enclave

sends the Secure Storage Component the passcode entropy. The Secure Storage

Component first increments the counter for the lockbox. If the incremented counter

exceeds the maximum attempt value, the Secure Storage Component completely erases

the counter lockbox. If the maximum attempt count hasn’t been reached, the Secure

Storage Component attempts to derive the passcode verifier value and lockbox entropy

value with the same algorithm used to create the counter lockbox. If the derived passcode

verifier value matches the stored passcode verifier value, the Secure Storage Component

returns the lockbox entropy value to the Secure Enclave and resets the counter to 0.

The keys used to access password-protected data are rooted in the entropy stored in

counter lockboxes. For more information, see Data Protection overview.

The secure non-volatile storage is used for all anti-replay services in the Secure Enclave.

Anti-replay services on the Secure Enclave are used for revocation of data over events that

mark anti-replay boundaries including, but not limited to, the following:

• Passcode change

• Enabling or disabling FaceID or TouchID

• Adding or removing a FaceID face or a TouchID fingerprint

• FaceID or TouchID reset

• Adding or removing an ApplePay card

• Erase All Content and Settings

On architectures that don’t feature a Secure Storage Component, EEPROM (electrically

erasable programmable read-only memory) is utilised to provide secure storage services

for the Secure Enclave. Just like the Secure Storage Components, the EEPROM is attached

and accessible only from the Secure Enclave, but it doesn’t contain dedicated hardware

security features, nor does it guarantee exclusive access to entropy (aside from its physical

attachment characteristics) or counter lockbox functionality.

16Apple Platform Security

Secure Neural Engine

On devices with FaceID, the Secure Neural Engine converts 2D images and depth maps

into a mathematical representation of a user’s face.

On A11 up to A13 SoCs, the Secure Neural Engine is integrated into the Secure Enclave.

TheSecure Neural Engine uses direct memory access (DMA) for high performance. An

input-output memory management unit (IOMMU) under the sepOS kernel’s control limits

this direct access to authorised memory regions.

Starting with A14 and the M1 family, the Secure Neural Engine is implemented as a secure

mode in the Application Processor’s Neural Engine. A dedicated hardware security

controller switches between Application Processor and Secure Enclave tasks, resetting

Neural Engine state on each transition to keep FaceID data secure. A dedicated engine

applies memory encryption, authentication and access control. At the same time, it uses

a separate cryptographic key and memory range to limit the Secure Neural Engine to

authorised memory regions.

Power and clock monitors

All electronics are designed to operate within a limited voltage and frequency envelope.

When operated outside this envelope, the electronics can malfunction and then security

controls may be bypassed. To help ensure that the voltage and frequency stay in a safe

range, the Secure Enclave is designed with monitoring circuits. These monitoring circuits

are designed to have a much larger operating envelope than the rest of the Secure

Enclave. If the monitors detect an illegal operating point, the clocks in the Secure Enclave

automatically stop and don’t restart until the next SoC reset.

Secure Enclave feature summary

Note: A12, A13, S4 and S5 products first released in autumn 2020 have a 2nd-generation

Secure Storage Component, whereas earlier products based on these SoCs have a

1st-generation Secure Storage Component.

SoC Memory Protection

Engine

Secure Storage AES Engine PKA

A8 Encryption and

authentication

EEPROM Yes No

A9 Encryption and

authentication

EEPROM DPA protection Yes

A10 Encryption and

authentication

EEPROM DPA protection and

lockable seed bits

OS-bound keys

A11 Encryption,

authentication and

replay prevention

EEPROM DPA protection and

lockable seed bits

OS-bound keys

A12 (Apple devices

released before

autumn 2020)

Encryption,

authentication and

replay prevention

Secure Storage

Component gen 1

DPA protection and

lockable seed bits

OS-bound keys

17Apple Platform Security

SoC Memory Protection

Engine

Secure Storage AES Engine PKA

A12 (Apple devices

released after

autumn 2020)

Encryption,

authentication and

replay prevention

Secure Storage

Component gen 2

DPA protection and

lockable seed bits

OS-bound keys

A13 (Apple devices

released before

autumn 2020)

Encryption,

authentication and

replay prevention

Secure Storage

Component gen 1

DPA protection and

lockable seed bits

OS-bound keys and

Boot Monitor

A13 (Apple devices

released after

autumn 2020)

Encryption,

authentication and

replay prevention

Secure Storage

Component gen 2

DPA protection and

lockable seed bits

OS-bound keys and

Boot Monitor

A14, A15 Encryption,

authentication and

replay prevention

Secure Storage

Component gen 2

DPA protection and

lockable seed bits

OS-bound keys and

Boot Monitor

S3 Encryption and

authentication

EEPROM DPA protection and

lockable seed bits

Yes

S4 Encryption,

authentication and

replay prevention

Secure Storage

Component gen 1

DPA protection and

lockable seed bits

OS-bound keys

S5 (Apple devices

released before

autumn 2020)

Encryption,

authentication and

replay prevention

Secure Storage

Component gen 1

DPA protection and

lockable seed bits

OS-bound keys

S5 (Apple devices

released after

autumn 2020)

Encryption,

authentication and

replay prevention

Secure Storage

Component gen 2

DPA protection and

lockable seed bits

OS-bound keys

S6, S7 Encryption,

authentication and

replay prevention

Secure Storage

Component gen 2

DPA protection and

lockable seed bits

OS-bound keys

T2 Encryption and

authentication

EEPROM DPA protection and

lockable seed bits

OS-bound keys

M1 Family Encryption,

authentication and

replay prevention

Secure Storage

Component gen 2

DPA protection and

lockable seed bits

OS-bound keys and

Boot Monitor

18Apple Platform Security

FaceID and TouchID

FaceID and TouchID security

Passcodes and passwords are essential to the security of Apple devices. At the same time,

users require convenient access to their devices, often more than a hundred times a day.

Biometric authentication provides a way to retain the security of a strong passcode — or

even strengthen the passcode or password because it need not be entered manually —

while providing the convenience of swiftly unlocking with a finger press or glance. FaceID

and TouchID don’t replace a passcode or password, but in most situations they do make

access faster and easier.

Apple’s biometric security architecture relies on a strict separation of responsibilities

between the biometric sensor and the Secure Enclave, and a secure connection between

the two. The sensor captures the biometric image and securely transmits it to the Secure

Enclave. During enrolment, the Secure Enclave processes, encrypts and stores the

corresponding FaceID and TouchID template data. During matching, the Secure Enclave

compares incoming data from the biometric sensor against the stored templates to

determine whether to unlock the device or respond that a match is valid (for ApplePay, in-

app purchases and other uses of FaceID and TouchID). The architecture supports devices

that include both the sensor and Secure Enclave (such as iPhone, iPad and many Mac

systems), as well as the ability to physically separate the sensor into a peripheral that is

then securely paired to the Secure Enclave in a Mac with Apple silicon.

FaceID security

With a simple glance, FaceID securely unlocks supported Apple devices. It provides

intuitive and secure authentication enabled by the TrueDepth camera system, which uses

advanced technologies to accurately map the geometry of a user’s face. FaceID uses

neural networks for determining attention, matching and anti-spoofing, so a user can

unlock their phone with a glance, even with a mask on when using supported devices.

FaceID automatically adapts to changes in appearance and carefully safeguards the

privacy and security of a user’s biometric data.

FaceID is designed to confirm user attention, provide robust authentication with a low

false-match rate and mitigate both digital and physical spoofing.

The TrueDepth camera automatically looks for the user’s face when the user wakes an

Apple device that features FaceID (by raising it or tapping the screen), as well as when

those devices attempt to authenticate the user in order to display an incoming notification

or when a supported app requests FaceID authentication. When a face is detected, FaceID

confirms attention and intent to unlock by detecting that the user’s eyes are open and

their attention is directed at their device. For accessibility, the FaceID attention check is

disabled when VoiceOver is activated and, if required, can be disabled separately. Attention

detection is always required when using FaceID with a mask.

19Apple Platform Security

After the TrueDepth camera confirms the presence of an attentive face, it projects and

reads thousands of infrared dots to form a depth map of the face along with a 2D infrared

image. This data is used to create a sequence of 2D images and depth maps which are

digitally signed and sent to the Secure Enclave. To counter both digital and physical

spoofs, the TrueDepth camera randomises the sequence of 2D images and depth map

captures and projects a device-specific random pattern. A portion of the Secure Neural

Engine — protected within the Secure Enclave — transforms this data into a mathematical

representation and compares that representation with the enrolled facial data. This

enrolled facial data is itself a mathematical representation of the user’s face captured

across a variety of poses.

TouchID security

TouchID is the fingerprint sensing system that makes secure access to supported Apple

devices faster and easier. This technology reads fingerprint data from any angle and

learns more about a user’s fingerprint over time, with the sensor continuing to expand the

fingerprint map as additional overlapping nodes are identified with each use.

Apple devices with a TouchID sensor can be unlocked using a fingerprint. TouchID doesn’t

replace the need for a device passcode or user password, which is still required after

device startup, restart or logout (on a Mac). In some apps, TouchID can also be used in

place of a device passcode or user password — for example, to unlock password-protected

notes in the Notes app, to unlock keychain-protected websites and to unlock supported

app passwords. However, a device passcode or user password is always required in some

scenarios (for example, to change an existing device passcode or user password or to

remove existing fingerprint enrolments or create new ones).

When the fingerprint sensor detects the touch of a finger, it triggers the advanced imaging

array to scan the finger and sends the scan to the Secure Enclave. The channel used to

secure this connection varies, depending on whether the TouchID sensor is built into the

device with the Secure Enclave or is located in a separate peripheral.

While the fingerprint scan is being vectorised for analysis, the raster scan is temporarily

stored in encrypted memory within the Secure Enclave and then it’s discarded. The

analysis uses subdermal ridge flow angle mapping, a lossy process that discards “finger

minutiae data” that would be required to reconstruct the user’s actual fingerprint. During

enrolment, the resulting map of nodes is stored in an encrypted format that can be read

only by the Secure Enclave as a template to compare against for future matches, but

without any identity information. This data never leaves the device. It’s not sent to Apple,

nor is it included in device backups.

Built-in TouchID channel security

Communication between the Secure Enclave and the built-in TouchID sensor takes place

over a serial peripheral interface bus. The processor forwards the data to the Secure

Enclave but can’t read it. It’s encrypted and authenticated with a session key that’s

negotiated using a shared key provisioned for each TouchID sensor and its corresponding

Secure Enclave at the factory. For every TouchID sensor, the shared key is strong, random

and different. The session key exchange uses AES key wrapping, with both sides providing

a random key that establishes the session key and uses transport encryption that provides

both authentication and confidentiality (using AES-CCM).

20Apple Platform Security

Magic Keyboard with TouchID

The Magic Keyboard with TouchID (and the Magic Keyboard with TouchID and Numeric

Keypad) provides a TouchID sensor in an external keyboard that can be used with any Mac

with Apple silicon. The Magic Keyboard with TouchID performs the role of the biometric

sensor; it doesn’t store biometric templates, perform biometric matching or enforce

security policies (for example, having to enter the password after 48 hours without an

unlock). The TouchID sensor in the Magic Keyboard with TouchID must be securely paired

to the Secure Enclave on the Mac before it can be used, and then the Secure Enclave

performs the enrolment and matching operations and enforces security policies in the

same way it would for a built-in TouchID sensor. Apple performs the pairing process in

the factory for a Magic Keyboard with TouchID that is shipped with a Mac. Pairing can

also be performed by the user if needed. A Magic Keyboard with TouchID can be securely

paired with only one Mac at a time, but a Mac can maintain secure pairings with up to five

different Magic Keyboard with TouchID keyboards.

The Magic Keyboard with TouchID and built-in TouchID sensors are compatible. If a finger

that was enrolled on a built-in Mac TouchID sensor is presented on a Magic Keyboard with

TouchID, the Secure Enclave in the Mac successfully processes the match — and vice versa.

To support secure pairing and thus communication between the Mac Secure Enclave and

the Magic Keyboard with TouchID, the keyboard is equipped with a hardware Public Key

Accelerator (PKA) block to provide attestation, and with hardware-based keys to perform

the necessary cryptographic processes.

Secure pairing

Before a Magic Keyboard with TouchID can be used for TouchID operations, it needs to

be securely paired to the Mac. To pair, the Secure Enclave on the Mac and the PKA block

in the Magic Keyboard with TouchID exchange public keys, rooted in the trusted ApplCA,

and they use hardware-held attestation keys and ephemeral ECDH to securely attest to

their identity. On the Mac, this data is protected by the Secure Enclave; on the Magic

Keyboard with TouchID, this data is protected by the PKA block. After secure pairing, all

TouchID data communicated between the Mac and the Magic Keyboard with TouchID is

encrypted by AES-GCM with a key length of 256 bits, and with ephemeral ECDH keys using

NIST P-256 curve based on the stored identities. (Normal keystrokes are exchanged using

Bluetooth security in the same way that any Bluetooth keyboard does.)

Secure intent to pair

To perform some TouchID operations for the first time, such as enrolling a new fingerprint,

the user must physically confirm their intent to use a Magic Keyboard with TouchID

with the Mac. Physical intent is confirmed by pressing twice on the Mac power button

when indicated by the user interface, or by successfully matching a fingerprint that

had previously been enrolled with the Mac. For more information, see Secure intent and

connections to the Secure Enclave.

ApplePay transactions can be authorised with a TouchID match or by entering the macOS

user password and pressing twice on the TouchID button on the Magic Keyboard with

TouchID. The latter allows the user to confirm physical intent even without a TouchID match.

21Apple Platform Security

Magic Keyboard with TouchID channel security

To help ensure a secure communication channel between the TouchID sensor in the Magic

Keyboard with TouchID and Secure Enclave on the paired Mac, the following are required:

• The secure pairing between the Magic Keyboard with TouchID PKA block and the

Secure Enclave as described above

• A secure channel between the Magic Keyboard with TouchID sensor and its PKA block

The secure channel between the Magic Keyboard with TouchID sensor and its PKA block is

established in the factory by using a unique key shared between the two. (This is the same

technique used to create the secure channel between the Secure Enclave on the Mac and

its built-in sensor for Mac computers with TouchID built-in.)

FaceID, TouchID, passcodes and passwords

To use FaceID or TouchID, the user must set up their device so that a passcode or

password is required to unlock it. When FaceID or TouchID detects a successful match,

the user’s device unlocks without asking for the device passcode or password. This makes

using a longer, more complex passcode or password far more practical because the user

doesn’t need to enter it as frequently. FaceID and TouchID don’t replace the user’s

passcode or password; instead, they provide easy access to the device within thoughtful

boundaries and time constraints. This is important because a strong passcode or password

forms the foundation for how a user’s iPhone, iPad, Mac or AppleWatch cryptographically

protects that user’s data.

When a device passcode or password is required

Users can use their passcode or password anytime instead of FaceID or TouchID, but

there are situations where biometrics aren’t permitted. The following security-sensitive

operations always require entry of a passcode or password:

• Updating the software

• Erasing the device

• Viewing or changing passcode settings

• Installing configuration profiles

• Unlocking the Security & Privacy pane in System Preferences on Mac

• Unlocking the Users & Groups pane in System Preferences on Mac (if FileVault is turned on)

22Apple Platform Security

A passcode or password is also required if the device is in any of the following states:

• The device has just been turned on or restarted

• The user has logged out of their Mac account (or hasn’t yet logged in).

• The user hasn’t unlocked their device for more than 48 hours.

• The user hasn’t used their passcode or password to unlock their device for 156 hours

(six and a half days), and the user hasn’t used a biometric to unlock their device in

4hours.

• The device has received a remote lock command

• The user exited power off / Emergency SOS by pressing and holding either volume button

and the Sleep/Wake button simultaneously for 2 seconds and then pressing Cancel.

• There were five unsuccessful biometric match attempts (though for usability, the device

might offer entering a passcode or password instead of using biometrics after a smaller

number of failures).

When FaceID with a mask is enabled on an iPhone, it’s available for the next 6.5 hours

after one of the following user actions:

• Successful FaceID match attempt (with or without a mask)

• Device passcode validation

• Device unlock with AppleWatch

Any of these actions extends the period by an additional 6.5 hours when performed.

When FaceID or TouchID is enabled on iPhone or iPad, the device immediately locks

when the Sleep/Wake button is pressed, and the device locks every time it goes to sleep.

FaceID and TouchID require a successful match — or optionally, use of the passcode — at

every wake.

The probability that a random person in the population could unlock a user’s iPhone or

iPad is less than 1 in 1,000,000 with FaceID — including when FaceID with a mask is

turnedon. For a user’s iPhone, iPad, and Mac models with TouchID and those paired with a

Magic Keyboard, it’s less than 1 in 50,000. This probability increases with multiple enrolled

fingerprints (up to 1 in 10,000 with five fingerprints) or appearances (up to 1 in 500,000

with two appearances). For additional protection, both FaceID and TouchID allow only five

unsuccessful match attempts before a passcode or password is required to obtain access

to the user’s device or account. With FaceID, the probability of a false match is higher for:

• Twins and siblings who look like the user

• Children under the age of 13 (because their distinct facial features may not have fully

developed)

The probability is further increased in these two cases when FaceID with a mask is used.

If a user is concerned about a false match, Apple recommends using a passcode to

authenticate.

23Apple Platform Security

Facial matching security

Facial matching is performed within the Secure Enclave using neural networks trained

specifically for that purpose. Apple developed the facial matching neural networks

using over a billion images, including infrared (IR) and depth images collected in studies

conducted with the participants’ informed consent. Apple then worked with participants

from around the world to include a representative group of people accounting for gender,

age, ethnicity and other factors. The studies were augmented as needed to provide a high

degree of accuracy for a diverse range of users. FaceID is designed to work with hats,

scarves, glasses, contact lenses and many types of sunglasses. FaceID also supports

unlocking with a mask on iPhone devices starting with iPhone 12 and iOS 15.4 or later.

Furthermore, it’s designed to work indoors, outdoors and even in total darkness. An

additional neural network — that’s trained to spot and resist spoofing — defends against

attempts to unlock the device with photos or masks. FaceID data, including mathematical

representations of a user’s face, is encrypted and available only to the Secure Enclave.

This data never leaves the device. It’s not sent to Apple, nor is it included in device

backups. The following FaceID data is saved, encrypted only for use by the Secure Enclave

during normal operation:

• The mathematical representations of a user’s face calculated during enrolment

• The mathematical representations of a user’s face calculated during some unlock

attempts if FaceID deems them useful to augment future matching

Face images captured during normal operation aren’t saved but are instead immediately

discarded after the mathematical representation is calculated for either enrolment or

comparison with the enrolled FaceID data.

Improving FaceID matches

To improve match performance and keep pace with the natural changes of a face and look,

FaceID augments its stored mathematical representation over time. Upon a successful

match, FaceID may use the newly calculated mathematical representation — if its quality

is sufficient — for a finite number of additional matches before that data is discarded.

Conversely, if FaceID fails to recognise a face but the match quality is higher than a certain

threshold and a user immediately follows the failure by entering their passcode, FaceID

takes another capture and augments its enrolled FaceID data with the newly calculated

mathematical representation. This new FaceID data is discarded if the user stops matching

against it or after a finite number of matches; the new data is also discarded when the

option to reset FaceID is selected. These augmentation processes allow FaceID to keep

up with dramatic changes in a user’s facial hair or makeup use while minimising false

acceptance.

24Apple Platform Security

Uses for FaceID and TouchID

Unlocking a device or user account

With FaceID or TouchID turned off, when a device or account locks, the keys for the

highest class of Data Protection — which are held in the Secure Enclave — are discarded.

The files and keychain items in that class are inaccessible until the user unlocks the device

or account by entering their passcode or password.

With FaceID or TouchID turned on, the keys aren’t discarded when the device or

account locks; instead, they’re wrapped with a key that’s given to the FaceID or TouchID

subsystem inside the Secure Enclave. When a user attempts to unlock the device or

account, if the device detects a successful match it provides the key for unwrapping

the Data Protection keys and the device or account is unlocked. This process provides

additional protection by requiring cooperation between the Data Protection and FaceID or

TouchID subsystems to unlock the device.

When the device restarts, the keys required for FaceID or TouchID to unlock the device or

account are lost; they’re discarded by the Secure Enclave after any condition is met that

requires passcode or password entry.

Securing purchases with ApplePay

The user can also use FaceID and TouchID with ApplePay to make easy and secure

purchases in shops, in apps and on the web:

• Using FaceID in shops: To authorise an in-store payment with FaceID, the user must

first confirm intent to pay by double-clicking the side button. This double-click captures

user intent using a physical gesture directly linked to the Secure Enclave and is resistant

to forgery by a malicious process. The user then authenticates using FaceID before

placing the device near the contactless payment reader. A different ApplePay payment

method can be selected after FaceID authentication, which requires re-authentication,

but the user won’t have to double-click the side button again.

• Using FaceID in apps and on the web: To make a payment within apps and on the

web, the user confirms their intent to pay by double-clicking the side button and then

authenticates using FaceID to authorise the payment. If the ApplePay transaction

isn’t completed within 60 seconds of double-clicking the side button, the user must

reconfirm intent to pay by double-clicking again.

• Using TouchID: For TouchID, the intent to pay is confirmed using the gesture of activating

the TouchID sensor combined with successfully matching the user’s fingerprint.

Using system-provided APIs

Third-party apps can use system-provided APIs to ask the user to authenticate using

FaceID or TouchID or a passcode or password, and apps that support TouchID

automatically support FaceID without any changes. When using FaceID or TouchID,

the app is notified only as to whether the authentication was successful; it can’t access

FaceID, TouchID or the data associated with the enrolled user.

25Apple Platform Security

Protecting keychain items

Keychain items can also be protected with FaceID or TouchID, to be released by the

Secure Enclave only by a successful match or with the device passcode or account

password. App developers have APIs to verify that a passcode or password has been set

by the user before requiring FaceID or TouchID or a passcode or password to unlock

keychain items. App developers can do any of the following:

• Require that authentication API operations don’t fall back to an app password or the

device passcode. They can query whether a user is enrolled, allowing FaceID or

TouchID to be used as a second factor in security-sensitive apps.

• Generate and use Elliptic Curve Cryptography (ECC) keys inside the Secure Enclave

that can be protected by FaceID or TouchID. Operations with these keys are always

performed inside the Secure Enclave after it authorises their use.

Making and approving purchases

Users can also configure FaceID or TouchID to approve purchases from the iTunesStore,

the AppStore, Apple Books and more, so they don’t have to enter their AppleID password.

When purchases are made, the Secure Enclave verifies that a biometric authorisation

occurred and then releases ECC keys used to sign the store request.

Secure intent and connections to the Secure Enclave

Secure intent provides a way to confirm a user’s intent without any interaction with the

operating system or Application Processor. The connection is a physical link — from a

physical button to the Secure Enclave — that’s available in the following:

• iPhone X or later

• AppleWatch Series 1 or later

• iPad Pro (all models)

• iPad Air (2020)

• Mac computers with Apple silicon

With this link, users can confirm their intent to complete an operation in a way designed

such that even software with root privileges or in the kernel can’t spoof.

This feature is used to confirm user intent during ApplePay transactions and when

finalising pairing Magic Keyboard with TouchID to a Mac with Apple silicon. A double-press

on the appropriate button (for FaceID) or a fingerprint scan (for TouchID) when prompted

by the user interface signals confirmation of user intent. For more information, see

Securing purchases with ApplePay. A similar mechanism — based on the Secure Enclave

and T2 firmware — is supported on MacBook models with the Apple T2 Security Chip and

no Touch Bar.

26Apple Platform Security

Hardware microphone disconnect

All Apple silicon–based Mac notebooks and Intel-based Mac notebooks with the Apple T2

Security Chip feature a hardware disconnect that disables the microphone whenever the

lid is closed. On all 13-inch MacBook Pro and MacBook Air notebooks with the T2 chip,

all MacBook notebooks with a T2 chip from 2019 or later, and Mac notebooks with Apple

silicon, this disconnect is implemented in hardware alone. The disconnect is designed

to prevent any software — even with root or kernel privileges in macOS, and even the

software on the T2 chip or other firmware — from engaging the microphone when the lid is

closed. (The camera isn’t disconnected in hardware because its field of view is completely

obstructed with the lid closed.)

iPad models from 2020 onwards also feature the hardware microphone disconnect. When

an MFi-compliant case (including those sold by Apple) is attached to the iPad and closed,

the microphone is disconnected in hardware. This is designed to prevent microphone audio

data being made available to any software — even with root or kernel privileges in iPadOS

or any device firmware.

The protections in this section are implemented directly with hardware logic, according to

the following circuit diagram:

In each product with a hardware microphone cutoff, one or more lid sensors detects

the physical closure of the lid or case using some physical property (for example, a Hall

effect sensor or a hinge angle sensor) of the interaction. For sensors where calibration is

necessary, parameters are set during production of the device and the calibration process

includes a non-reversible hardware lockout of any subsequent changes to sensitive

parameters on the sensor. These sensors emit a direct hardware signal that goes through

a simple set of non-reprogrammable hardware logic. This logic provides debounce,

hysteresis and/or a delay of up to 500ms before disabling the microphone. Depending on

the product, this signal can be implemented either by disabling the lines transporting data

between the microphone and the System on Chip (SoC) or by disabling one of the input

lines to the microphone module that’s allowing it to be active — for example, the clock line

or a similar effective control.

27Apple Platform Security

Express Cards with power reserve

If iOS isn’t in use because iPhone needs to be charged, there may still be enough power in

the battery to support Express Card transactions. Supported iPhone devices automatically

support this feature with:

• A payment or travel card designated as the Express Travel card

• Student ID cards with Express Mode turned on

• Car keys with Express Mode turned on

• Home keys with Express Mode turned on

• Hospitality or Corporate access cards with Express Mode turned on

Pressing the side button (or on iPhone SE 2nd generation, the Home button), displays the

low-battery icon as well as text indicating that Express Cards are available to use. The

NFC controller performs Express Card transactions under the same conditions as when

iOS is in use, except that transactions are indicated only with haptic notification (no visible

notification is shown). On iPhone SE 2nd generation, completed transactions may take a

few seconds to appear onscreen. This feature isn’t available when a standard user-initiated

shutdown is performed.

28Apple Platform Security

System security

System security overview

Building on the unique capabilities of Apple hardware, system security is responsible for

controlling access to system resources in Apple devices without compromising usability.

System security encompasses the boot-up process, software updates, and protection

of computer system resources such as CPU, memory, disk, software programs and

stored data.

The most recent versions of Apple operating systems are the most secure. An important

part of Apple security is secure boot, which protects the system from malware infection

at boot time. Secure boot begins in hardware and builds a chain of trust through software,

where each step is designed to ensure that the next is functioning properly before handing

over control. This security model supports not only the default boot of Apple devices, but

also the various modes for recovery and timely updates on Apple devices. Subcomponents

like the T2 Chip and the Secure Enclave also perform their own secure boot to help

ensure they only boot known-good code from Apple. The update system is designed to

prevent downgrade attacks, so that devices can’t be rolled back to an older version of the

operating system (which an attacker knows how to compromise) as a method of stealing

user data.

Apple devices also include boot and runtime protections so they maintain their integrity

during ongoing operation. Apple-designed silicon on iPhone, iPad, AppleWatch, AppleTV,

HomePod and a Mac with Apple silicon provide a common architecture for protecting

operating system integrity. macOS also features an expanded and configurable set of

protection capabilities in support of its differing computing model, as well as capabilities

supported on all Mac hardware platforms.

Secure boot

Boot process for iOS and iPadOS devices

Each step of the startup process contains components that are cryptographically signed

by Apple to enable integrity checking so that the boot proceeds only after verifying the

chain of trust. These components include the bootloaders, the kernel, kernel extensions

and mobile baseband firmware. This secure boot chain is designed to verify that the lowest

levels of software aren’t tampered with.

29Apple Platform Security

When an iOS or iPadOS device is turned on, its Application Processor immediately executes

code from read-only memory referred to as Boot ROM. This immutable code, known as

the hardware root of trust, is laid down during chip fabrication and is implicitly trusted.

The Boot ROM code contains the Apple Root certificate authority (CA) public key — used

to verify that the iBoot bootloader is signed by Apple before allowing it to load. This is the

first step in the chain of trust, in which each step checks that the next is signed by Apple.

When the iBoot finishes its tasks, it verifies and runs the iOS or iPadOS kernel. For devices

with an A9 or earlier A-series processor, an additional Low Level Bootloader (LLB) stage is

loaded and verified by the Boot ROM, which in turn loads and verifies iBoot.

A failure to load or verify following stages is handled differently depending on the

hardware:

• Boot ROM can’t load LLB (older devices): Device Firmware Upgrade (DFU) mode

• LLB or iBoot: Recovery mode

In either case, the device must be connected to the Finder (macOS 10.15 or later) or iTunes

(macOS 10.14 or earlier) through USB and restored to factory default settings.

The Boot Progress Register (BPR) is used by the Secure Enclave to limit access to user

data in different modes and is updated before entering the following modes:

• DFU mode: Set by Boot ROM on devices with Apple A12 or later SoCs

• Recovery mode: Set by iBoot on devices with Apple A10, S2 or later SoCs

On devices with mobile access, a mobile baseband subsystem performs additional secure

booting using signed software and keys verified by the baseband processor.

The Secure Enclave also performs a secure boot that checks its software (sepOS) is

verified and signed by Apple.

Memory safe iBoot implementation

In iOS14 and iPadOS 14, Apple modified the C compiler toolchain used to build the iBoot

bootloader to improve its security. The modified toolchain implements code designed to

prevent memory- and type-safety issues that are typically encountered in C programs. For

example, it helps prevent most vulnerabilities in the following classes:

• Buffer overflows, by ensuring that all pointers carry bounds information that is verified

when accessing memory

• Heap exploitation, by separating heap data from its metadata and accurately detecting

error conditions such as double free errors

• Type confusion, by ensuring that all pointers carry runtime type information that’s

verified during pointer cast operations

• Type confusion caused by use after free errors, by segregating all dynamic memory

allocations by static type

This technology is available on iPhone with Apple A13 Bionic or later, and iPad with the A14

Bionic chip.

30Apple Platform Security

Mac computers with Apple silicon

Boot process for a Mac with Apple silicon

When a Mac with Apple silicon is turned on, it performs a boot process much like that of

iPhone and iPad.

The chip executes code from the Boot ROM in the first step in the chain of trust. macOS

secure boot on a Mac with Apple silicon verifies not only the operating system code itself,

but also the security policies and even kexts (supported, though not recommended)

configured by authorised users.

When LLB (Low Level Bootstrap) is launched, it then verifies the signatures and loads

system-paired firmware for intra-SoC cores such as the storage, display, system

management and Thunderbolt controllers. LLB is also responsible for loading the

LocalPolicy, which is a file signed by the Secure Enclave Processor. The LocalPolicy file

describes the configuration that the user has chosen for the system boot and runtime

security policies. The LocalPolicy has the same data structure format as all other boot

objects, but it’s signed locally by a private key that’s available only within a particular

computer’s Secure Enclave instead of being signed by a central Apple server (like software

updates).

To help prevent replay of any previous LocalPolicy, LLB must look up a nonce from the

Secure Enclave–attached Secure Storage Component. To do this, it uses the Secure

Enclave Boot ROM and makes sure the nonce in the LocalPolicy matches the nonce in the

Secure Storage Component. This helps prevent an old LocalPolicy — which could have

been configured for lower security — from being reapplied to the system after security has

been upgraded. The result is that secure boot on a Mac with Apple silicon helps protect

not only against rollback of operating system versions but also against security policy

downgrades.

31Apple Platform Security

The LocalPolicy file captures whether the operating system is configured for Full, Reduced

or Permissive security.

• Full Security: The system behaves like iOS and iPadOS, and allows only booting

software that was known to be the latest that was available at install time.

• Reduced Security: LLB is directed to trust “global” signatures, which are bundled with

the operating system. This allows the system to run older versions of macOS. Because

older versions of macOS inevitably have unpatched vulnerabilities, this security mode

is described as Reduced. This is also the policy level required to support booting kernel

extensions (kexts).

• Permissive Security: The system behaves like Reduced Security in that it uses global

signature verification for iBoot and beyond, but it also tells iBoot that it should accept

some boot objects being signed by the Secure Enclave with the same key used to sign

the LocalPolicy. This policy level supports users that are building, signing and booting

their own custom XNU kernels.

If the LocalPolicy indicates to LLB that the selected operating system is running in Full

Security, LLB evaluates the personalised signature for iBoot. If it’s running in Reduced

Security or Permissive Security, it evaluates the global signature. Any signature verification

errors cause the system to boot to recoveryOS to provide repair options.

After LLB hands off to iBoot, it loads macOS-paired firmware such as that for the Secure

Neural Engine, the Always On Processor and other firmware. iBoot also looks at information

about the LocalPolicy handed to it from LLB. If the LocalPolicy indicates that there should

be an Auxiliary Kernel Collection (AuxKC), iBoot looks for it on the file system, verifies that

it was signed by the Secure Enclave with the same key as the LocalPolicy, and verifies that

its hash matches a hash stored in the LocalPolicy. If the AuxKC is verified, iBoot places it

into memory with the Boot Kernel Collection before locking the full memory region covering

the Boot Kernel Collection and AuxKC with the System Coprocessor Integrity Protection

(SCIP). If the policy indicates that an AuxKC should be present but it isn’t found, the

system continues to boot into macOS without it. iBoot is also responsible for verifying the

root hash for the signed system volume (SSV) to check that the file system the kernel will

mount is fully integrity verified.

32Apple Platform Security

Boot modes for a Mac with Apple silicon

A Mac with Apple silicon has the boot modes described below.

Mode Key combo Description

macOS From a shutdown state, press

and release the power button.

1. Boot ROM hands off to LLB.

2. LLB loads system-paired firmware and the Local Policy

for the selected macOS.

3. LLB locks an indication into the Boot Progress

hands off to i Boot.

4. i Boot loads the macOS-paired firmware, the static

trust cache, the device tree and the Boot Kernel

Collection.

5. If the Local Policy allows it, i Boot loads the Auxiliary

Kernel Collection (Aux KC) of third-party kexts.

6. If the Local Policy didn’t disable it, i Boot verifies the

root signature hash for the signed system volume

(SSV).

Paired recovery OS From a shutdown state, press

and hold the power button.

1. Boot ROM hands off to LLB.

2. LLB loads system-paired firmware and the Local Policy

for the recovery OS.

3. LLB locks an indication into the Boot Progress

hands off to i Boot for paired recovery OS.

4. i Boot loads the macOS-paired firmware, the trust

cache, the device tree and the Boot Kernel Collection.

5. If paired recovery OS boot fails, booting into fallback

recovery OS is attempted.

Note: Security downgrades aren’t allowed on the paired

recovery OS Local Policy.

Fallback recovery OS From a shutdown state,

double-press and hold the

power button.

1. Boot ROM hands off to LLB.

2. LLB loads system-paired firmware and the Local Policy

for the recovery OS.

3. LLB locks an indication into the Boot Progress

hands off to i Boot for recovery OS.

4. i Boot loads the macOS-paired firmware, the trust

cache, the device tree and the Boot Kernel Collection.

Note: Security downgrades aren’t allowed on the paired

recovery OS Local Policy.

Safe mode Boot into recovery OS per the

above, then hold Shift while

selecting the startup volume.

1. Boots to recovery OS as per the above.

2. Holding the Shift key while selecting a volume causes

the Boot Picker app to approve that macOS for

booting, as normal; it also sets an nvram variable that

tells i Boot to not load the Aux KC on the next boot.

3. System reboots and boots to the targeted volume, but

i Boot doesn’t load Aux KC.

33Apple Platform Security

Paired recoveryOS restrictions

In macOS 12.0.1 or later, every new macOS installation also installs a paired version of

recoveryOS into the corresponding APFS volume group. This design is familiar to users

of Intel-based Mac computers, but on a Mac with Apple silicon, it provides additional

security and compatibility guarantees. Because every macOS installation now has a

dedicated paired recoveryOS, this helps ensure that only that dedicated paired recoveryOS

can perform security-downgrading operations. This helps protect installations of newer

versions of macOS from tampering initiated from older versions of macOS, and vice versa.

The pairing restrictions are enforced as follows:

• All installations of macOS11 are paired to the recoveryOS. If a macOS11 installation is

selected to boot by default, the recoveryOS is booted by holding down the power key at

boot time on a Mac with Apple silicon. The recoveryOS can downgrade security settings

of any macOS11 installations, but not any installations of macOS 12.0.1.

• If a macOS 12.0.1 or later installation is selected to boot by default, its paired

recoveryOS is booted by holding down the power key when the Mac starts up. The

paired recoveryOS can downgrade security settings for the paired macOS installation,

but not for any other macOS installation.

To boot into a paired recoveryOS for any macOS installation, that installation needs to

be selected as the default, which is done using Startup Disk in System Preferences or by

starting any recoveryOS and holding Option while selecting a volume.

Note: Fallback recoveryOS can’t perform downgrades for any macOS installations.

Startup Disk security policy control for a Mac with Apple silicon

Overview

Unlike security policies on an Intel-based Mac, security policies on a Mac with Apple

silicon are for each installed operating system. This means that multiple installed macOS

instances with different versions and security policies are supported on the same Mac. For

this reason, an operating system picker has been added to Startup Security Utility.

On a Mac with Apple silicon, System Security Utility indicates the overall user-configured

security state of macOS, such as the booting of a kext or the configuration of System

Integrity Protection (SIP). If changing a security setting would significantly degrade

security or make the system easier to compromise, users must enter into recoveryOS

by holding the power button (so that malware can’t trigger the signal, only a human with

physical access can) to make the change. Because of this, an Apple silicon–based Mac also

won’t require (or support) a firmware password — all critical changes are already gated by

user authorisation. For more information on SIP, see System Integrity Protection.

34Apple Platform Security

Full Security and Reduced Security can be set using Startup Security Utility from

recoveryOS. But Permissive Security can be accessed only from command-line tools for

users who accept the risk of making their Mac much less secure.

Full Security policy

Full Security is the default and it behaves like iOS and iPadOS. At the time software is

downloaded and prepared to install, rather than using the global signature that comes with

the software, macOS contacts the same Apple signing server used for iOS and iPadOS and

requests a fresh, “personalised” signature. A signature is personalised when it includes the

Exclusive Chip Identification (ECID) — a unique ID specific to the Apple CPU in this case—

as part of the signing request. The signature given back by the signing server is then

unique and usable only by that particular Apple CPU. When the Full Security policy is in

effect, the Boot ROM and LLB helps ensure that a given signature isn’t just signed by Apple

but is signed for this specific Mac, essentially tying that version of macOS to that Mac.

Using an online signing server also provides better protection against rollback attacks

than typical global signature approaches. In a global signing system, the security epoch

could have rolled many times but a system that has never seen the latest firmware won’t

know this. For example, a computer that currently believes it’s in security epoch 1 accepts

software from security epoch 2, even if the current actual security epoch is 5. With an

Apple silicon online signing system, the signing server can reject creating signatures for

software that’s in anything except the latest security epoch.

Additionally, if an attacker discovers a vulnerability after a security epoch change, they

can’t simply pick up the vulnerable software from a previous epoch off system A and

apply it to system B in order to attack it. The fact that the vulnerable software from an

older epoch was personalised to system A helps prevent it from being transferable and

thus being used to attack system B. All these mechanisms work together to provide much

stronger guarantees that attackers can’t purposely place vulnerable software on a Mac in

order to circumvent the protections provided by the latest software. But a user that’s in

possession of an administrator username and password for the Mac can always choose the

security policy that works best for their use cases.

35Apple Platform Security

Reduced Security policy

Reduced Security is similar to Medium Security behaviour on an Intel-based Mac with a

T2 chip, in which a vendor (in this case, Apple) generates a digital signature for the code

to assert it came from the vendor. This design helps prevent attackers from inserting

unsigned code. Apple refers to this signature as a “global” signature because it can be

used on any Mac, for any amount of time, for a Mac that currently has a Reduced Security

policy set. Reduced security doesn’t itself provide protection against rollback attacks

(although unauthorised operating system changes can result in user data being rendered

inaccessible. For more information, see Kernel extensions in a Mac with Apple silicon.

In addition to enabling users to run older versions of macOS, Reduced Security is required

for other actions that can put a user’s system security at risk, such as introducing third-

party kernel extensions (kexts). Kexts have the same privileges as the kernel, and thus

any vulnerabilities in third-party kexts can lead to full operating system compromise. This

is why developers are being strongly encouraged to adopt system extensions before kext

support is removed from macOS for future Mac computers with Apple silicon. Even when

third-party kexts are enabled, they can’t be loaded into the kernel on demand. Instead,

the kexts are merged into an Auxiliary Kernel Collection (AuxKC) — whose hash is stored

in the LocalPolicy — and thus they require a reboot. For more information about AuxKC

generation, see Kernel extensions in macOS.

Permissive Security policy

Permissive Security is for users who accept the risk of putting their Mac into a much more

insecure state. This mode differs from No Security mode on an Intel-based Mac with a T2

chip. With Permissive Security, signature verification is still performed along the entire

secure boot chain, but setting the policy to Permissive signals to iBoot that it should

accept locally Secure Enclave–signed boot objects, such as a user-generated Boot Kernel

Collection built from a custom XNU kernel. This way, Permissive Security also provides an

architectural capability for running an arbitrary “fully untrusted operating system” kernel.

When a custom Boot Kernel Collection or fully untrusted operating system is loaded on

the system, some decryption keys become unavailable. This is designed to prevent fully

untrusted operating systems from accessing data from trusted operating systems.

36Apple Platform Security

Important: Apple doesn’t provide or support custom XNU kernels.

There’s another way that Permissive Security differs from No Security on an Intel-based

Mac with a T2 chip: it’s a prerequisite for some security downgrades that in the past have

been independently controllable. Most notably, to disable System Integrity Protection (SIP)

on a Mac with Apple silicon, a user must acknowledge that they’re putting the system into

Permissive Security. This is required because disabling SIP has always put the system into

a state that makes the kernel much easier to compromise. In particular, disabling SIP on a

Mac with Apple silicon disables kext signature enforcement during AuxKC generation time,

thus allowing any arbitrary kext to be loaded into kernel memory. Another improvement to

SIP that’s been made on a Mac with Apple silicon is that the policy store has been moved

out of NVRAM and into the LocalPolicy. So now, disabling SIP requires authentication by a

user who has access to the LocalPolicy signing key from recoveryOS (reached by pressing

and holding the power button). This makes it significantly more difficult for a software-only

attacker, or even a physically present attacker, to disable SIP.

It isn’t possible to downgrade to Permissive Security from the Startup Security Utility app.

Users can downgrade only by running command-line tools from Terminal in recoveryOS,

such as csrutil (to disable SIP). After the user has downgraded, the fact that it’s

occurred is reflected in Startup Security Utility, and so a user can easily set the security to

a more secure mode.

Note: A Mac with Apple silicon doesn’t require or support a specific media boot policy

because technically all boots are performed locally. If a user chooses to boot from external

media, that operating system version must first be personalised using an authenticated

reboot from recoveryOS. This reboot creates a LocalPolicy file on the internal drive that’s

used to perform a trusted boot from the operating system stored on the external media.

This means the configuration of booting from external media is always explicitly enabled

on a per-operating system basis, and already requires user authorisation, so no additional

secure configuration is necessary.

37Apple Platform Security

LocalPolicy signing-key creation and management

Creation

When macOS is first installed in the factory, or when a tethered erase-install is performed,

the Mac runs code from temporary restore RAM disk to initialise the default state. During

this process, the restore environment creates a new pair of public and private keys,

which are held in the Secure Enclave. The private key is referred to as the Owner Identity

Key (OIK). If any OIK already exists, it’s destroyed as part of this process. The restore

environment also initialises the key used for Activation Lock; the User Identity Key (UIK).

Part of that process that is unique to a Mac with Apple silicon is when UIK certification is

requested for Activation Lock, a set of requested constraints to be enforced at validation-

time on the LocalPolicy are included. If the device can’t get a UIK certified for Activation

Lock (for example, because the device is currently associated with a Find My Mac account

and reported as lost), it’s unable to proceed further to create a LocalPolicy. If a device

is issued a User identity Certificate (ucrt), that ucrt contains server-imposed policy

constraints and user-requested policy constraints in an X.509 v3 extension.

When an Activation Lock/ucrt is successfully retrieved, it’s stored in a database on the

server side and also returned to the device. After the device has a ucrt, a certification

request for the public key that corresponds to the OIK is sent to the Basic Attestation

Authority (BAA) server. BAA verifies the OIK certification request using the public key from

the ucrt stored in the BAA accessible database. If the BAA can verify the certification, it

certifies the public key, returning the Owner Identity Certificate (OIC), which is signed by

the BAA and contains the constraints stored in ucrt. The OIC is sent back to the Secure

Enclave. From then on, whenever the Secure Enclave signs a new LocalPolicy, it attaches

the OIC to the Image4. LLB has built-in trust in the BAA root certificate, which causes it to

trust the OIC, which causes it to trust the overall LocalPolicy signature.

RemotePolicy constraints

All Image4 files, not just Local Policies, contain constraints on Image4 manifest evaluation.

These constraints are encoded using special object identifiers (OIDs) in the leaf certificate.

The Image4 verification library looks up the special certificate constraint OID from a

certificate during signature evaluation and then mechanically evaluates the constraints

specified in it. The constraints are of the form:

• X must exist

• X must not exist

• X must have a specific value

So, for instance, for “personalised” signatures, the certificate constraints will contain

“ECID must exist”, and for “global” signatures, it will contain “ECID must not exist”. These

constraints are designed to ensure that all Image4 files signed by a given key must

conform to certain requirements to avoid erroneous signed Image4 manifest generation.

38Apple Platform Security

In the context of each LocalPolicy, these Image4 certificate constraints are referred to

as the RemotePolicy. A different RemotePolicy can exist for different boot environments’

LocalPolicies. The RemotePolicy is used to restrict the recoveryOS LocalPolicy so that

when recoveryOS is booted it can only ever behave as if it’s booting with Full Security. This

increases trust in the integrity of the recoveryOS boot environment as a place where policy

can be changed. The RemotePolicy restricts the LocalPolicy to contain the ECID of the

Mac on which the LocalPolicy was generated, and the specific Remote Policy Nonce Hash

(rpnh) stored in the Secure Storage Component on that Mac. The rpnh, and therefore the

RemotePolicy, change only when actions are taken for Find My Mac and Activation Lock,

such as enrolment, unenrolment, remote lock and remote wipe. RemotePolicy constraints

are determined and specified at User Identity Key (UIK) certification time and are signed

in to the issued User identity Certificate (ucrt). Some RemotePolicy constraints, such as

ECID, ChipID and BoardID, are determined by the server. This is designed to prevent one

device from signing LocalPolicy files for another device. Other RemotePolicy constraints

may be specified by the device to help prevent Security downgrade of the LocalPolicy

without providing both the local authentication required to access the current OIK and

remote authentication of the account to which the device is Activation Locked.

Contents of a LocalPolicy file for a Mac with Apple silicon

The LocalPolicy is an Image4 file signed by the Secure Enclave. Image4 is an ASN.1

(Abstract Syntax Notation One) DER-encoded data structure format that’s used to describe

information about secure boot chain objects on Apple platforms. In an Image4-based

secure boot model, security policies are requested at software installation time initiated

by a signing request to a central Apple signing server. If the policy was acceptable, the

signing server returns a signed Image4 file containing a variety of four-character code

(4CC) sequences. These signed Image4 files and 4CCs are evaluated at startup by

software like the Boot ROM or LLB.

Ownership handoff between operating systems

Access to the Owner Identity Key (OIK) is referred to as “Ownership”. Ownership is required

to allow users to re-sign the LocalPolicy after making policy or software changes. The OIK

is protected with the same key hierarchy as described in Sealed Key Protection (SKP), with

the OIK being protected by the same Key encryption key (KEK) as the Volume encryption

key (VEK). This means it’s normally protected by both user passwords and measurements

of the operating system and policy. There’s only a single OIK for all operating systems on

the Mac. Therefore, when installing a second operating system, explicit consent is required

from the users on the first operating system to hand off Ownership to the users on the

second operating system. However, users don’t yet exist for the second operating system

when the installer is running from the first operating system. Users in operating systems

aren’t normally generated until the operating system is booted and the Setup Assistant

is running. Therefore, two new actions are required when installing a second operating

system on a Mac with Apple silicon:

• Creating a LocalPolicy for the second operating system

• Preparing an “Install User” for handing off Ownership

39Apple Platform Security

When running an Install Assistant and targeting installation for a secondary blank volume,

a prompt asks the user if they’d like to copy a user from the current volume to be the

first user of the second volume. If the user says yes, the “Install User” that is created

is, in reality, a KEK derived from the selected user’s password and hardware keys, which

is then used to encrypt the OIK as it’s being handed to the second operating system.

Then from within the second operating system Install Assistant, it prompts for that user’s

password to allow it to access the OIK in the Secure Enclave for the new operating system.

If users opt not to copy a user, the Install User is still created the same way, but an empty

password is used instead of a user’s password. This second flow exists for certain system

administration scenarios. However, users who want to have multi-volume installs and

perform Ownership handoff in the most secure fashion should always opt to copy a user

from the first operating system to the second operating system.

LocalPolicy on a Mac with Apple silicon

For a Mac with Apple silicon, local security policy control has been delegated to an

application running in the Secure Enclave. This software can utilise the user’s credentials

and the boot mode of the primary CPU to determine who can change the security policy

and from what boot environment. This helps prevent malicious software from using the

security policy controls against the user by downgrading them to gain more privileges.

LocalPolicy manifest properties

The LocalPolicy file contains some architectural 4CCs that are found in almost all Image4

files — such as a board or model ID (BORD), indicating a particular Apple chip (CHIP) or

Exclusive Chip Identification (ECID). But the 4CCs below focus only on the security policies

that users can configure.

Note: Apple uses the term Paired One True recoveryOS (1TR) to indicate a boot into the

paired recoveryOS using a physical power button single-press-and-hold. This differs from

a normal recoveryOS boot, which happens using NVRAM or double-press-and-hold, or

which may happen when errors occur on startup. The physical button press of a specific

kind increases trust in that the boot environment isn’t reachable by a software-only

attacker who has broken into macOS.

LocalPolicy Nonce Hash (lpnh)

• Type: OctetString (48)

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The lpnh is used for anti-replay of the LocalPolicy. This is an SHA384

hash of the LocalPolicy Nonce (LPN), which is stored in the Secure Storage Component

and accessible using the Secure Enclave Boot ROM or Secure Enclave. The raw nonce

is never visible to the Application Processor, only to the sepOS. An attacker wanting

to convince LLB that a previous LocalPolicy they had captured was valid would need

to place a value into the Secure Storage Component, which hashes to the same lpnh

value found in the LocalPolicy they want to replay. Normally, there is a single LPN valid

on the system — except during software updates, when two are simultaneously valid —

to allow for the possibility of falling back to booting the old software in the event of an

update error. When any LocalPolicy for any operating system is changed, all policies are

re-signed with the new lpnh value corresponding to the new LPN found in the Secure

Storage Component. This change happens when the user changes security settings or

creates new operating systems with a new LocalPolicy for each.

40Apple Platform Security

RemotePolicy Nonce Hash (rpnh)

• Type: OctetString (48)

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The rpnh behaves the same way as the lpnh but is updated only when the

remote policy is updated, such as when changing the state of Find My enrolment. This

change happens when the user changes the state of Find My on their Mac.

recoveryOS Nonce Hash (ronh)

• Type: OctetString (48)

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The ronh behaves the same way as the lpnh, but is found exclusively in

the LocalPolicy for system recoveryOS. It’s updated when the system recoveryOS is

updated, such as on software updates. A separate nonce from the lpnh and rpnh is

used so that when a device is put into a disabled state by Find My, existing operating

systems can be disabled (by removing their LPN and RPN from the Secure Storage

Component), while still leaving the system recoveryOS bootable. In this way, the

operating systems can be re-enabled when the system owner proves their control over

the system by putting in their iCloud password used for the Find My account. This

change happens when a user updates the system recoveryOS or creates new operating

systems.

Next Stage Image4 Manifest Hash (nsih)

• Type: OctetString (48)

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The nsih field represents an SHA384 hash of the Image4 manifest data

structure that describes the booted macOS. The macOS Image4 manifest contains

measurements for all the boot objects — such as iBoot, the static trust cache, device

tree, Boot Kernel Collection and signed system volume (SSV) volume root hash. When

LLB is directed to boot a given macOS, it’s designed to ensure that the hash of the

macOS Image4 manifest attached to iBoot matches what’s captured in the nsih field

of the LocalPolicy. In this way, the nsih captures the user intention of what operating

system the user has created a LocalPolicy for. Users change the nsih value implicitly

when they perform a software update.

Auxiliary Kernel Collection (AuxKC) Policy Hash (auxp)

• Type: OctetString (48)

• Mutable environments: macOS

• Description: The auxp is an SHA384 hash of the user-authorised kext list (UAKL) policy.

This is used at AuxKC generation time to help ensure that only user-authorised kexts

are included in the AuxKC. smb2 is a prerequisite for setting this field. Users change

the auxp value implicitly when they change the UAKL by approving a kext from the

Security& Privacy pane in System Preferences.

41Apple Platform Security

Auxiliary Kernel Collection (AuxKC) Image4 Manifest Hash (auxi)

• Type: OctetString (48)

• Mutable environments: macOS

• Description: After the system verifies that the UAKL hash matches what’s found in

the auxp field of the LocalPolicy, it requests that the AuxKC be signed by the Secure

Enclave processor application that’s responsible for LocalPolicy signing. Next, an

SHA384 hash of the AuxKC Image4 manifest signature is placed into the LocalPolicy to

avoid the potential for mixing and matching previously signed AuxKCs to an operating

system at boot time. If iBoot finds the auxi field in the LocalPolicy, it attempts to load

the AuxKC from storage and validate its signature. It also verifies that the hash of the

Image4 manifest attached to the AuxKC matches the value found in the auxi field. If

the AuxKC fails to load for any reason, the system continues to boot without this boot

object and so without any third-party kexts loaded. The auxp field is a prerequisite for

setting the auxi field in the LocalPolicy. Users change the auxi value implicitly when

they change the UAKL by approving a kext from the Security & Privacy pane in System

Preferences.

Auxiliary Kernel Collection (AuxKC) Receipt Hash (auxr)

• Type: OctetString (48)

• Mutable environments: macOS

• Description: The auxr is an SHA384 hash of the AuxKC receipt, which indicates the

exact set of kexts that were included into the AuxKC. The AuxKC receipt can be a

subset of the UAKL, because kexts can be excluded from the AuxKC even if they’re

user authorised if they’re known to be used for attacks. In addition, some kexts that can

be used to break the user-kernel boundary may lead to decreased functionality, such

as an inability to use ApplePay or play 4K and HDR content. Users who want these

capabilities opt in to a more restrictive AuxKC inclusion. The auxp field is a prerequisite

for setting the auxr field in the LocalPolicy. Users change the auxr value implicitly

when they build a new AuxKC from the Security & Privacy pane in System Preferences.

CustomOS Image4 Manifest Hash (coih)

• Type: OctetString (48)

• Mutable environments: 1TR

• Description: The coih is an SHA384 hash of CustomOS Image4 manifest. The payload

for that manifest is used by iBoot (instead of the XNU kernel) to transfer control.

Users change the coih value implicitly when they use the kmutil configure-boot

command-line tool in 1TR.

APFS volume group UUID (vuid)

• Type: OctetString (16)

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The vuid indicates the volume group the kernel should use as root. This

field is primarily informational and isn’t used for security constraints. This vuid is set

by the user implicitly when creating a new operating system install.

42Apple Platform Security

Key encryption key (KEK) Group UUID (kuid)

• Type: OctetString (16)

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The kuid indicates the volume that was booted. The key encryption key

has typically been used for Data Protection. For each LocalPolicy, it’s used to protect

the LocalPolicy signing key. The kuid is set by the user implicitly when creating a new

operating system install.

Paired recoveryOS Trusted Boot Policy Measurement (prot)

• Type: OctetString (48)

• Mutable environments: 1TR, recoveryOS, macOS

• Description: A paired recoveryOS Trusted Boot Policy Measurement (TBPM) is a special

iterative SHA384 hash calculation over the Image4 manifest of a LocalPolicy, excluding

nonces, in order to give a consistent measurement over time (because nonces like lpnh

are frequently updated). The prot field, which is found only in each macOS LocalPolicy,

provides a pairing to indicate the recoveryOS LocalPolicy that corresponds to the

macOS LocalPolicy.

Has Secure Enclave Signed recoveryOS LocalPolicy (hrlp)

• Type: Boolean

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The hrlp indicates whether or not the prot value (above) is the

measurement of a Secure Enclave–signed recoveryOS LocalPolicy. If not, then the

recoveryOS LocalPolicy is signed by the Apple online signing server, which signs things

such as macOS Image4 files.

Local Operating System Version (love)

• Type: Boolean

• Mutable environments: 1TR, recoveryOS, macOS

• Description: The love indicates the OS version that the LocalPolicy is created for. The

version is obtained from the next state manifest during LocalPolicy creation and is used

to enforce recoveryOS pairing restrictions.

Secure Multi-Boot (smb0)

• Type: Boolean

• Mutable environments: 1TR, recoveryOS

• Description: If smb0 is present and true, LLB allows the next stage Image4 manifest to

be globally signed instead of requiring a personalised signature. Users can change this

field with Startup Security Utility or bputil to downgrade to Reduced Security.

43Apple Platform Security

Secure Multi-Boot (smb1)

• Type: Boolean

• Mutable environments: 1TR

• Description: If smb1 is present and true, iBoot allows objects such as a custom kernel

collection to be Secure Enclave signed with the same key as the LocalPolicy. Presence

of smb0 is a prerequisite for presence of smb1. Users can change this field using

command-line tools such as csrutil or bputil to downgrade to Permissive Security.

Secure Multi-Boot (smb2)

• Type: Boolean

• Mutable environments: 1TR

• Description: If smb2 is present and true, iBoot allows the Auxiliary Kernel Collection to

be Secure Enclave signed with the same key as the LocalPolicy. The presence of smb0

is a prerequisite for the presence of smb2. Users can change this field using Startup

Security Utility or bputil to downgrade to Reduced Security and enable third-party

kexts.

Secure Multi-Boot (smb3)

• Type: Boolean

• Mutable environments: 1TR

• Description: If smb3 is present and true, a user at the device has opted in to mobile

device management (MDM) control of their system. Presence of this field makes

the LocalPolicy-controlling Secure Enclave processor application accept MDM

authentication instead of requiring local user authentication. Users can change this field

using Startup Security Utility or bputil to enable managed control over third-party

kexts and software updates. (In macOS 11.2 or later, MDM can also initiate an update to

the latest macOS version if the current security mode is Full Security.)

Secure Multi-Boot (smb4)

• Type: Boolean

• Mutable environments: macOS

• Description: If smb4 is present and true, the device has opted in to MDM control of

the operating system using the Apple School Manager, Apple Business Manager or

Apple Business Essentials. Presence of this field makes the LocalPolicy-controlling

Secure Enclave application accept MDM authentication instead of requiring local

user authentication. This field is changed by the MDM solution when it detects that a

device’s serial number appears in any of those three services.

System Integrity Protection (sip0)

• Type: 64 bit unsigned integer

• Mutable environments: 1TR

• Description: The sip0 holds the existing System Integrity Protection (SIP) policy bits

that previously were stored in NVRAM. New SIP policy bits are added here (instead of

using LocalPolicy fields like the below) if they’re used only in macOS and not used by

LLB. Users can change this field using csrutil from 1TR to disable SIP and downgrade

to Permissive Security.

44Apple Platform Security

System Integrity Protection (sip1)

• Type: Boolean

• Mutable environments: 1TR

• Description: If sip1 is present and true, iBoot will allow failures to verify the SSV

volume root hash. Users can change this field using csrutil or bputil from 1TR.

System Integrity Protection (sip2)

• Type: Boolean

• Mutable environments: 1TR

• Description: If sip2 is present and true, iBoot will not lock the Configurable Text Read-

only Region (CTRR) hardware register that marks kernel memory as non-writable. Users

can change this field using csrutil or bputil from 1TR.

System Integrity Protection (sip3)

• Type: Boolean

• Mutable environments: 1TR

• Description: If sip3 is present and true, iBoot will not enforce its built-in allow list for

the boot-args NVRAM variable, which would otherwise filter the options passed to the

kernel. Users can change this field using csrutil or bputil from 1TR.

Certificates and RemotePolicy

As described in LocalPolicy signing-key creation and management, the LocalPolicy Image4

also contains the Owner Identity Certificate (OIC) and the embedded RemotePolicy.

45Apple Platform Security

Intel-based Mac computers

Boot process for an Intel-based Mac

Intel-based Mac with an Apple T2 Security Chip

When an Intel-based Mac computer with the Apple T2 Security Chip is turned on, the

chip performs a secure boot from its Boot ROM in the same fashion as iPhone, iPad and a

Mac with Apple silicon. This verifies the iBoot bootloader and is the first step in the chain

of trust. iBoot checks the kernel and kernel extension code on the T2 chip, which then

checks the Intel UEFI firmware. The UEFI firmware and the associated signature are initially

available only to the T2 chip.

After verification, the UEFI firmware image is mapped into a portion of the T2 chip memory.

This memory is made available to the Intel CPU through the enhanced Serial Peripheral

Interface (eSPI). When the Intel CPU first boots, it fetches the UEFI firmware through the eSPI

from the integrity-checked, memory-mapped copy of the firmware located on the T2 chip.

The evaluation of the chain of trust continues on the Intel CPU, with the UEFI firmware

evaluating the signature for boot.efi, which is the macOS bootloader. The Intel-resident

macOS secure boot signatures are stored in the same Image4 format used for iOS, iPadOS

and T2 chip secure boot, and the code that parses the Image4 files is the same hardened

code from the current iOS and iPadOS secure boot implementation. Boot.efi in turn verifies

the signature of a new file, called immutablekernel. When secure boot is enabled, the

immutablekernel file represents the complete set of Apple kernel extensions required to

boot macOS. The secure boot policy terminates at the handoff to the immutablekernel and,

after that, macOS security policies (such as System Integrity Protection and signed kernel

extensions) take effect.

46Apple Platform Security

If there are any errors or failures in this process, the Mac enters Recovery mode, Apple

T2 Security Chip Recovery mode or Apple T2 Security Chip Device Firmware Upgrade

(DFU) mode.

Microsoft Windows on an Intel-based Mac with a T2 chip

By default, an Intel-based Mac that supports secure boot trusts only content signed by

Apple. However, to improve the security of Boot Camp installations, Apple also supports

secure booting for Windows. The Unified Extensible Firmware Interface (UEFi) firmware

includes a copy of the Microsoft Windows Production CA 2011 certificate used to

authenticate Microsoft bootloaders.

Note: There is currently no trust provided for the Microsoft Corporation UEFI CA 2011 that

would allow verification of code signed by Microsoft partners. This UEFI CA is commonly

used to verify the authenticity of bootloaders for other operating systems such as Linux

variants.

Support for secure boot of Windows isn’t enabled by default; instead, it’s enabled using

Boot Camp Assistant (BCA). When a user runs BCA, macOS is reconfigured to trust

Microsoft first-party signed code during boot. After BCA completes, if macOS fails to

pass the Apple first-party trust evaluation during secure boot, the UEFI firmware attempts

to evaluate the trust of the object according to UEFI secure boot formatting. If the trust

evaluation succeeds, the Mac proceeds and boots Windows. If not, the Mac enters

recoveryOS and informs the user of the trust evaluation failure.

Intel-based Mac computers without a T2 chip

An Intel-based Mac without a T2 chip doesn’t support secure boot. Therefore, the Unified

Extensible Firmware Interface (UEFi) firmware loads the macOS booter (boot.efi) from the

file system without verification, and the booter loads the kernel (prelinkedkernel) from the

file system without verification. To protect the integrity of the boot chain, users should

enable all of the following security mechanisms:

• System Integrity Protection (SIP): Enabled by default, this protects the booter and

kernel against malicious writes from within a running macOS.

• FileVault: This can be enabled in two ways: by the user or by a mobile device

management (MDM) administrator. This protects against a physically present attacker

using Target Disk Mode to overwrite the booter.

• Firmware Password: This can be enabled in two ways: by the user or by an MDM

administrator. This helps prevent a physically present attacker from launching

alternative boot modes such as recoveryOS, Single User Mode or Target Disk Mode

from which the booter can be overwritten. This also helps prevent booting from

alternative media, by which an attacker could run code to overwrite the booter.

47Apple Platform Security

Boot modes of an Intel-based Mac with an Apple T2 Security Chip

An Intel-based Mac with an Apple T2 Security Chip has a variety of boot modes that can

be entered at boot time by pressing key combinations, which are recognised by the UEFI

firmware or booter. Some boot modes, such as Single User Mode, won’t work unless the

security policy is changed to No Security in Startup Security Utility.

Mode Key combo Description

macOS boot None The UEFI firmware hands off to the macOS booter

(a UEFI application), which hands off to the macOS

kernel. On standard booting of a Mac with File Vault

enabled, the macOS booter presents the Login Window

interface, which takes the password to decrypt the

storage.

Startup Manager Option (⌥)The UEFI firmware launches the built-in UEFI

application that presents the user with a boot device

selection interface.

Target Disk Mode

(TDM)

TThe UEFI firmware launches the built-in UEFI

application that exposes the internal storage device

as a raw, block-based storage device over Fire Wire,

Thunderbolt, USB or any combination of the three

(depending on the Mac model).

Single User Mode Command (⌘)-S The macOS kernel passes the -s flag in launchd’s

argument vector, then launchd creates the single-user

shell in the Console app’s tty.

Note: If the user exits the shell, macOS continues boot

to the Login Window.

recovery OS Command (⌘)-R The UEFI firmware loads a minimal macOS from a

signed disk image (.dmg) file on the internal storage

device.

Internet recovery OS Option (⌥)-Command (⌘)-R The signed disk image is downloaded from the internet

using HTTP.

Diagnostics DThe UEFI firmware loads a minimal UEFI diagnostic

environment from a signed disk image file on the

internal storage device.

Internet Diagnostics Option (⌥)-D The signed disk image is downloaded from the internet

using HTTP.

Windows boot None If Windows has been installed using Boot Camp, the

UEFI firmware hands off to the Windows booter, which

hands off to the Windows kernel.

48Apple Platform Security

Startup Security Utility on a Mac with an Apple T2 Security Chip

Overview

On an Intel-based Mac with an Apple T2 Security Chip, Startup Security Utility handles a

number of security policy settings. The utility is accessible by booting into recoveryOS and

selecting Startup Security Utility from the Utilities menu and protects supported security

settings from easy manipulation by an attacker.

Critical policy changes require authentication, even in Recovery mode. When Startup Security

Utility is first opened, it prompts the user to enter an administrator password from the primary

macOS installation associated with the currently booted recoveryOS. If no administrator

exists, one must be created before the policy can be changed. The T2 chip requires that

the Mac computer be currently booted into recoveryOS and that an authentication with a

Secure Enclave–backed credential has occurred before such a policy change can be made.

Security policy changes have two implicit requirements. RecoveryOS must:

• Be booted from a storage device directly connected to the T2 chip, because partitions

on other devices don’t have Secure Enclave–backed credentials bound to the internal

storage device.

• Reside on an APFS-based volume, because there is support only for storing the

Authentication in Recovery credentials sent to the Secure Enclave on the “Preboot”

APFS volume of a drive. HFS plus-formatted volumes can’t use secure boot.

This policy is shown only in Startup Security Utility on an Intel-based Mac with a T2 chip.

Although most use cases shouldn’t require changes to the secure boot policy, users are

ultimately in control of their device’s settings and may choose, depending on their needs,

to disable or downgrade the secure boot functionality on their Mac.

Secure boot policy changes made from within this app apply only to the evaluation of the

chain of trust being verified on the Intel processor. The option “Secure boot the T2 chip” is

always in effect.

Secure boot policy can be configured to one of three settings: Full Security, Medium

Security and No Security. No Security completely disables secure boot evaluation on the

Intel processor and allows the user to boot whatever they want.

49Apple Platform Security

Full Security boot policy

Full Security is the default boot policy, and it behaves much like iOS and iPadOS or Full

Security on a Mac with Apple silicon. At the time that software is downloaded and prepared

to install, it is personalised with a signature that includes the Exclusive Chip Identification

(ECID) — a unique ID specific to the T2 chip in this case — as part of the signing request.

The signature given back by the signing server is then unique and usable only by that

particular T2 chip. The Unified Extensible Firmware Interface (UEFi) firmware is designed to

ensure that when the Full Security policy is in effect, a given signature isn’t just signed by

Apple but is signed for this specific Mac, essentially tying that version of macOS to that Mac.

This helps prevent rollback attacks as described for Full Security on a Mac with Apple silicon.

Medium Security boot policy

Medium Security boot policy is somewhat like a traditional UEFI secure boot, in which

a vendor (here, Apple) generates a digital signature for the code to assert it came from

the vendor. This way, attackers are prevented from inserting unsigned code. We refer to

this signature as a “global” signature because it can be used on any Mac, for any amount

of time, for a Mac that currently has a Medium Security policy set. Neither iOS, iPadOS

nor the T2 chip itself support global signatures. This setting doesn’t attempt to prevent

rollback attacks.

Media boot policy

Media boot policy exists only on an Intel-based Mac with a T2 chip and is independent of

the secure boot policy. So even if a user disables secure boot, this doesn’t change the

default behaviour of preventing anything other than the storage device directly connected

to the T2 chip to boot the Mac. Media boot policy is not required on a Mac with Apple

silicon. For more information, see Startup Disk security policy control.

Firmware password protection in an Intel-based Mac

macOS on Intel-based Mac computers with an Apple T2 Security Chip supports the use

of a Firmware Password to help prevent unintended modifications of firmware settings

on a specific Mac. The Firmware Password is designed to prevent selecting alternative

boot modes such as booting into recoveryOS or Single User Mode, booting from an

unauthorised volume or booting into Target Disk Mode.

Note: The firmware password isn’t required on a Mac with Apple silicon because the critical

firmware functionality it restricted has been moved into the recoveryOS and (when FileVault

is enabled) recoveryOS requires user authentication before its critical functionality can be

reached.

The most basic mode of firmware password can be reached from the recoveryOS Firmware

Password Utility on an Intel-based Mac without a T2 chip, and from the Startup Security

Utility on an Intel-based Mac with a T2 chip. Advanced options (such as the ability to

prompt for the password at every boot) are available from the firmwarepasswd command-

line tool in macOS.

Setting a Firmware Password is especially important to reduce the risk of attacks on Intel-

based Mac computers without a T2 chip from a physically present attacker. The Firmware

Password can help prevent an attacker from booting to recoveryOS, from where they could

otherwise disable System Integrity Protection (SIP). And by restricting boot of alternative

media, an attacker can’t execute privileged code from another operating system to attack

peripheral firmwares.

50Apple Platform Security

A firmware password reset mechanism exists to help users who forget their password.

Users press a key combination at startup, and are presented with a model-specific string

to provide to AppleCare. AppleCare digitally signs a resource that is signature checked by

the Uniform Resource Identifier (URI). If the signature is validated and the content is for the

specific Mac, the UEFI firmware removes the firmware password.

For users who want no one but themselves to remove their firmware password by

software means, the -disable-reset-capability option has been added to the

firmwarepasswd command-line tool in macOS 10.15. Before setting this option, users

must acknowledge that if the password is forgotten and needs removal, the user must

bear the cost of the logic board replacement necessary to achieve this. Organisations that

want to protect their Mac computers from external attackers and from employees must set

a firmware password on organisation-owned systems. This can be accomplished on the

device in any of the following ways:

• At provisioning time, by manually using the firmwarepasswd command-line tool

• With third-party management tools that use the firmwarepasswd command-line tool

• Using mobile device management (MDM)

recoveryOS and diagnostics environments for an Intel-based Mac

recoveryOS

The recoveryOS is completely separate from the main macOS and the entire contents

are stored in a disk image file named BaseSystem.dmg. There is also an associated

BaseSystem.chunklist, which is used to verify the integrity of the BaseSystem.dmg. The

chunklist is a series of hashes for 10MB chunks of the BaseSystem.dmg. The Unified

Extensible Firmware Interface (UEFi) firmware evaluates the signature of the chunklist file

and then evaluates the hash one chunk at a time from the BaseSystem.dmg. This helps

ensure that it matches the signed content present in the chunklist. If any of these hashes

don’t match, booting from the local recoveryOS is aborted and the UEFI firmware attempts

to boot from Internet recoveryOS instead.

If the verification is successfully completed, the UEFI firmware mounts the BaseSystem.

dmg as a RAM disk and launches the boot.efi file that’s in it. There’s no need for the UEFI

firmware to do a specific check of the boot.efi, nor for the boot.efi to do a check of the

kernel, because the completed contents of the operating system (of which these elements

are only a subset) have already been integrity checked.

Apple Diagnostics

The procedure for booting the local diagnostic environment is mostly the same as

launching the recoveryOS. Separate AppleDiagnostics.dmg and AppleDiagnostics.chunklist

files are used, but they’re verified in the same way as the BaseSystem files. Instead of

launching boot.efi, the UEFI firmware launches a file inside the disk image (.dmg file)

named diags.efi, which is in turn responsible for invoking a variety of other UEFI drivers

that can interface with and check for errors in the hardware.

51Apple Platform Security

Internet recoveryOS and diagnostic environment

If an error has occurred in the launching of the local recovery or diagnostic environments,

the UEFI firmware attempts to download the images from the internet instead. (A user

can also specifically request the images to be fetched from the internet using special

key sequences held at boot.) The integrity validation of the disk images and chunklists

downloaded from the OS Recovery Server is performed the same way as with images

retrieved from a storage device.

While the connection to the OS Recovery Server is done using HTTP, the complete

downloaded contents are still integrity checked as previously described, and as such are

protected against manipulation by an attacker with control of the network. In the event

that an individual chunk fails integrity verification, it is re-requested from the OS Recovery

Server 11 times, before giving up and displaying an error.

When the internet recovery and diagnostic modes were added to Mac computers in 2011, it

was decided that it would be better to use the simpler HTTP transport and handle content

authentication using the chunklist mechanism, rather than implement the more complicated

HTTPS functionality in the UEFI firmware and thus increase the firmware’s attack surface.

Signed system volume security in iOS, iPadOS

andmacOS

In macOS 10.15, Apple introduced the read-only system volume, a dedicated, isolated

volume for system content. macOS11 or later adds strong cryptographic protections to

system content with a signed system volume (SSV). SSV features a kernel mechanism that

verifies the integrity of the system content at runtime and rejects any data — code and

non-code — without a valid cryptographic signature from Apple. Starting in iOS15 and

iPadOS 15, the system volume on an iOS and iPadOS device also gains the cryptographic

protection of a signed system volume.

SSV not only helps prevent tampering with any Apple software that’s part of the operating

system, it also makes macOS software updates more reliable and much safer. And because

SSV uses APFS (Apple File System) snapshots, if an update can’t be performed, the old

system version can be restored without reinstallation.

Since its introduction, APFS has provided file-system metadata integrity using non-

cryptographic checksums on the internal storage device. SSV strengthens the integrity

mechanism by adding cryptographic hashes, thus extending it to encompass every byte

of file data. Data from the internal storage device (including file-system metadata) is

cryptographically hashed in the read path, and the hash is then compared with an expected

value in the file-system metadata. In case of mismatch, the system assumes the data has

been tampered with and won’t return it to the requesting software.

Each SSV SHA256 hash is stored in the main file-system metadata tree, which is itself

hashed. And because each node of the tree recursively verifies the integrity of the hashes

of its children — similar to a binary hash (Merkle) tree — the root node’s hash value,

called a seal, therefore encompasses every byte of data in the SSV, which means the

cryptographic signature covers the entire system volume.

52Apple Platform Security

During macOS installation and update, the seal is recomputed from the file system on

device and that measurement is verified against the measurement Apple signed. On a

Mac with Apple silicon, the bootloader verifies the seal before transferring control to the

kernel. On an Intel-based Mac with an Apple T2 Security Chip, the bootloader forwards

the measurement and signature to the kernel, which then verifies the seal directly before

mounting the root file system. In either case, if the verification fails, the startup process

halts and the user is prompted to reinstall macOS. This procedure is repeated at every boot

unless the user has elected to enter a lower security mode and has separately chosen to

disable the signed system volume.

During iOS and iPadOS software updates, the system volume is prepared and recomputed

in a similar fashion. The iOS and iPadOS bootloaders verify that the seal is intact and that it

matches an Apple-signed value before allowing the device to start the kernel. Mismatches

at boot prompt the user to update the system software on the device. Users aren’t allowed

to disable the protection of a signed system volume on iOS and iPadOS.

SSV and code signing

Code signing is still present and enforced by the kernel. The signed system volume provides

protection when any bytes at all are read from the internal storage device. In contrast, code

signing provides protection when Mach objects are memory mapped as executable. Both

SSV and code signing protect executable code on all read and execute paths.

SSV and FileVault

In macOS 11, equivalent at-rest protection for system content is provided by the SSV, and

therefore the system volume no longer needs to be encrypted. Any modifications made to

the file system while it’s at rest will be detected by the file system when they’re read. If the

user has enabled FileVault, the user’s content on the data volume is still encrypted with a

user-provided secret.

If the user chooses to disable the SSV, the system at rest becomes vulnerable to

tampering, and this tampering could enable an attacker to extract encrypted user data

when the system next starts up. Therefore the system won’t permit the user to disable the

SSV if FileVault is enabled. Protection while at rest must be enabled or disabled for both

volumes in a consistent manner.

In macOS 10.15 or earlier, FileVault protects operating system software while at rest by

encrypting user and system content with a key protected by a user-provided secret.

This protects against an attacker with physical access to the device from accessing or

effectively modifying the file system containing system software.

SSV and a Mac with an Apple T2 Security Chip

On a Mac with an Apple T2 Security Chip, only macOS itself is protected by the SSV. The

software that runs on the T2 chip and verifies macOS is protected by secure boot.

53Apple Platform Security

Secure software updates

Security is a process; it isn’t enough to reliably boot the operating system version installed

at the factory — there must also exist a mechanism to quickly and securely obtain the

latest security updates. Apple regularly releases software updates to address emerging

security concerns. Users of iOS and iPadOS devices receive update notifications on the

device. Mac users find available updates in System Preferences. Updates are delivered

wirelessly, for rapid adoption of the latest security fixes.

The update process

The update process uses the same hardware-based root of trust that secure boot uses

and is designed to install only Apple-signed code. The update process also uses system

software authorisation to check that only copies of operating system versions that are

actively being signed by Apple can be installed on iOS and iPadOS devices or on Mac

computers with the Full Security setting configured as the secure boot policy in Startup

Security Utility. With these secure processes in place, Apple can stop signing older

operating system versions with known vulnerabilities and help prevent downgrade attacks.

For greater software update security, when the device to be upgraded is physically

connected to a Mac, a full copy of iOS or iPadOS is downloaded and installed. But for over-

the-air (OTA) software updates, only the components required to complete an update are

downloaded, improving network efficiency by not downloading the entire operating system.

What’s more, software updates can be cached on a Mac with macOS 10.13 or later with

Content Caching turned on, so that iOS and iPadOS devices don’t need to re-download the

necessary update over the internet. (They still need to contact Apple servers to complete

the update process.)

Personalised update process

During upgrades and updates, a connection is made to the Apple installation authorisation

server, which includes a list of cryptographic measurements for each part of the

installation bundle to be installed (for example, iBoot, the kernel and the operating system

image), arandom anti-replay value (the nonce) and the device’s unique Exclusive Chip

Identification (ECID).

54Apple Platform Security

The authorisation server checks the presented list of measurements against versions

whose installation is permitted and, if it finds a match, adds the ECID to the measurement

and signs the result. The server passes a complete set of signed data to the device as

part of the upgrade process. Adding the ECID “personalises” the authorisation for the

requesting device. By authorising and signing only for known measurements, the server

helps ensure that the update takes place exactly as Apple provided.

The boot-time chain-of-trust evaluation verifies that the signature comes from Apple and

that the measurement of the item loaded from the storage device, combined with the

device’s ECID, matches what was covered by the signature. These steps are designed to

ensure that, on devices that support personalisation, the authorisation is for a specific

device and that an older operating system or firmware version from one device can’t be

copied to another. The nonce helps prevent an attacker from saving the server’s response

and using it to tamper with a device or otherwise alter the system software.

The personalisation process is why a network connection to Apple is always required to

update any device with Apple-designed silicon, including an Intel-based Mac with the

Apple T2 Security Chip.

Finally, the user’s data volume is never mounted during a software update to help prevent

anything being read from or written to that volume during updates.

On devices with the Secure Enclave, that hardware similarly uses system software

authorisation to check the integrity of its software and is designed to prevent downgrade

installations.

55Apple Platform Security

Operating system integrity

Apple’s operating system software is designed with security at its core. This design

includes a hardware root of trust — leveraged to enable secure boot — and a secure

software update process that’s quick and safe. Apple’s operating systems also use their

purpose-built silicon-based hardware capabilities to help prevent exploitation as the

system runs. These runtime features protect the integrity of trusted code while it is being

executed. In short, Apple’s operating system software helps mitigate attack and exploit

techniques — whether those originate from a malicious app, from the web or through any

other channel. Protections listed here are available on devices with supported Apple-

designed SoCs, including iOS, iPadOS, tvOS, watchOS, and now macOS on a Mac with

Apple silicon.

Feature A10 A11, S3 A12, S4 A13, S5 A14, A15,

S6, S7

M1 Family

Kernel

Integrity

Protection

Fast

Permission

Restrictions



System

Coprocessor

Integrity

Protection

 

Pointer

Authentication

Codes

 

Page

Protection

Layer

See Note

below.

Note: Page Protection Layer (PPL) requires that the platform execute only signed and

trusted code; this is a security model that isn’t applicable on macOS.

Kernel Integrity Protection

After the operating system kernel completes initialisation, Kernel Integrity Protection (KIP)

is enabled to help prevent modifications of kernel and driver code. The memory controller

provides a protected physical memory region that iBoot uses to load the kernel and kernel

extensions. After startup is complete, the memory controller denies writes to the protected

physical memory region. The Application Processor’s Memory Management Unit (MMU)

is configured to help prevent mapping privileged code from physical memory outside the

protected memory region and to help prevent writeable mappings of physical memory

within the kernel memory region.

To prevent reconfiguration, the hardware used to enable KIP is locked after the boot

process is complete.

56Apple Platform Security

Fast Permission Restrictions

Starting with the Apple A11 Bionic and S3 SoCs, a new hardware primitive was introduced.

This primitive, Fast Permission Restrictions, includes a CPU register that quickly restricts

permissions per thread. With Fast Permission Restrictions (also known as APRR registers),

supported operating systems can remove execute permissions from memory without the

overhead of a system call and a page table walk or flush. These registers provide one more

level of mitigation for attacks from the web — particularly for code compiled at runtime

(just-in-time compiled) — because memory can’t be effectively executed at the same time

it’s being read from and written to.

System Coprocessor Integrity Protection

Coprocessor firmware handles many critical system tasks — for example, the Secure

Enclave, the image sensor processor and the motion coprocessor. Therefore its security

is a key part of the security of the overall system. To prevent modification of coprocessor

firmware, Apple uses a mechanism called System Coprocessor Integrity Protection (SCIP).

SCIP works much like Kernel Integrity Protection (KIP): at boot time, iBoot loads each

coprocessor’s firmware into a protected memory region, one that’s reserved and separate

from the KIP region. iBoot configures each coprocessor’s memory unit to help prevent:

• Executable mappings outside its part of the protected memory region

• Writable mappings inside its part of the protected memory region

Also at boot time, to configure SCIP for the Secure Enclave, the Secure Enclave operating

system is used. After the boot process is complete, the hardware used to enable SCIP is

locked. This is designed to prevent reconfiguration.

Pointer Authentication Codes

Pointer Authentication Codes (PACs) are used to protect against exploitation of memory

corruption bugs. System software and built-in apps use PAC to help prevent modification

of function pointers and return addresses (code pointers). PAC uses five secret 128-bit

values to sign kernel instructions and data, and each user space process has its own B

keys. Items are salted and signed as indicated below.

Item Key Salt

Function Return Address IB Storage address

Function Pointers IA 0

Block Invocation Function IA Storage address

Objective-C Method Cache IB Storage address + Class + Selector

C++ V-Table Entries IA Storage address + Hash (mangled

method name)

Computed Goto Label IA Hash (function name)

Kernel Thread State GA •

User Thread State Registers IA Storage address

C++ V-Table Pointers DA 0

57Apple Platform Security

The signature value is stored in the unused padding bits at the top of the 64-bit pointer.

The signature is verified before use and the padding is restored to help ensure a

functioning pointer address. Failure to verify results in an abort. This verification increases

the difficulty of many attacks, such as a return-oriented programming (ROP) attack, which

attempts to trick the device into executing existing code maliciously by manipulating

function return addresses stored on the stack.

Page Protection Layer

Page Protection Layer (PPL) in iOS, iPadOS and watchOS is designed to prevent user

space code from being modified after code signature verification is complete. Building

on Kernel Integrity Protection and Fast Permission Restrictions, PPL manages the page

table permission overrides to make sure only the PPL can alter protected pages containing

user code and page tables. The system provides a massive reduction in attack surface by

supporting system-wide code integrity enforcement, even in the face of a compromised

kernel. This protection isn’t offered in macOS because PPL is only applicable on systems

where all executed code must be signed.

Additional macOS system security capabilities

macOS operates on a broader set of hardware (for example, Intel-based CPUs, Intel-based

CPUs in combination with the Apple T2 Security Chip, and Apple silicon–based SoCs)

and supports a range of general-purpose computing use cases. Whereas some users use

only the basic pre-installed apps or those available from the AppStore, others are kernel

hackers who need to disable essentially all platform protections so they can run and test

their executing code as with the highest levels of trust. Most fall somewhere between and

many of those have peripherals and software that require varying levels of access. Apple

designed the macOS platform with an integrated approach to hardware, software and

services — a platform that provides security by design and makes it simple to configure,

deploy and manage, but that retains the configurability that users expect. macOS also

includes the key security technologies that an IT professional needs to help protect

corporate data and integrate within secure enterprise networking environments.

The following capabilities support and help secure the varied needs of macOS users.

Theyinclude:

• Signed system volume security

• System Integrity Protection

• Trust caches

• Protection for peripherals

• Rosetta 2 (automatic translation) support and security for a Mac with Apple silicon

• DMA support and protections

• Kernel extension (kext) support and security

• Option ROM support and security

• UEFI firmware security for Intel-based Mac computers

58Apple Platform Security

System Integrity Protection

macOS utilises kernel permissions to limit writability of critical system files with a feature

called System Integrity Protection (SIP). This feature is separate and in addition to the

hardware-based Kernel Integrity Protection (KIP) available on a Mac with Apple silicon,

which protects modification of the kernel in memory. Mandatory access control technology

is leveraged to provide this and a number of other kernel-level protections, including

sandboxing and Data Vault.

Mandatory access controls

macOS uses mandatory access controls — policies that set security restrictions, created

by the developer, that can’t be overridden. This approach is different from discretionary

access controls, which permit users to override security policies according to their

preferences.

Mandatory access controls aren’t visible to users but they’re the underlying technology

that helps enable several important features, including sandboxing, parental controls,

managed preferences, extensions and System Integrity Protection.

System Integrity Protection

System Integrity Protection restricts components to read-only in specific critical file

system locations to help prevent malicious code from modifying them. System Integrity

Protection is a computer-specific setting that’s on by default when a user upgrades to

OS X 10.11 or later. On an Intel-based Mac, disabling it removes protection for all partitions

on the physical storage device. macOS applies this security policy to every process

running on the system, regardless of whether it’s running sandboxed or with administrative

privileges.

Trust caches

One of the objects included in the Secure Boot chain is the static trust cache, a trusted

record of all the Mach-O binaries that are mastered into the signed system volume. Each

Mach-O is represented by a code directory hash. For efficient searching, these hashes are

sorted before being inserted into the trust cache. The code directory is the result of the

signing operation performed by codesign(1). To enforce the trust cache, SIP must remain

enabled. To disable trust cache enforcement on a Mac with Apple silicon, secure boot must

be configured to Permissive Security.

When a binary is executed (whether as part of spawning a new process or mapping

executable code into an existing process), its code directory is extracted and hashed. If the

resulting hash is found in the trust cache, the executable mappings created for the binary

will be granted platform privileges — that is, they may possess any entitlement and execute

without further verification as to the authenticity of the signature. This is in contrast to

an Intel-based Mac, where platform privileges are conveyed to operating system content

by the Apple certificate that signs the binaries. (This certificate doesn’t constrain which

entitlements the binary may possess.)

59Apple Platform Security

Non-platform binaries (for example, notarised third-party code) must have valid certificate

chains in order to execute, and the entitlements they may possess are constrained by the

signing profile issued to the developer by the Apple Developer Programme.

All binaries shipped within macOS are signed with a platform identifier. On a Mac with

Apple silicon, this identifier is used to indicate that even though the binary is signed by

Apple, its code directory hash must be present in the trust cache in order to execute. On an

Intel-based Mac, the platform identifier is used to perform targeted revocation of binaries

from an older release of macOS; this targeted revocation helps prevent those binaries from

executing on newer versions.

The static trust cache completely locks a set of binaries to a given version of macOS. This

behaviour helps prevent legitimately Apple-signed binaries from older operating systems

from being introduced into newer ones in order for an attacker to gain advantage.

Platform code shipped outside the operating system

Apple ships some binaries — for example, Xcode and the development tools stack — that

aren’t signed with a platform identifier. Even so, they’re still permitted to execute with

platform privileges on a Mac with Apple silicon and those with a T2 chip. Because this

platform software is shipped independently of macOS, it isn’t subject to the revocation

behaviours imposed by the static trust cache.

Loadable trust caches

Apple ships certain software packages with loadable trust caches. These caches have the

same data structure as the static trust cache. But although there’s only one static trust

cache — and its contents are always guaranteed to be locked into read-only ranges after

the kernel’s early initialisation is complete — loadable trust caches are added to the system

at runtime.

These trust caches are authenticated either through the same mechanism that

authenticates boot firmware (personalisation using the Apple trusted signing service), or as

globally signed objects (whose signatures don’t bind them to a particular device).

One example of a personalised trust cache is the cache shipped with the disk image

that’s used to perform field diagnostics on a Mac with Apple silicon. This trust cache is

personalised along with the disk image and loaded into the subject Mac computer’s kernel

while it’s booted into a diagnostic mode. The trust cache allows the software within the

disk image to run with platform privilege.

An example of a globally signed trust cache is shipped with macOS software updates. This

trust cache permits a chunk of code within the software update — the update brain — to

run with platform privilege. The update brain performs any work to stage the software

update that the host system lacks the capacity to perform in a consistent fashion across

versions.

60Apple Platform Security

Peripheral processor security in Mac computers

All modern computing systems have many built-in peripheral processors dedicated to tasks

such as networking, graphics, power management and more. These peripheral processors

are often single-purpose and are much less powerful than the primary CPU. Built-in

peripherals that don’t implement sufficient security become an easier target for attackers

to exploit, through which they can persistently infect the operating system. Having infected

a peripheral processor firmware, an attacker could target software on the primary CPU or

directly capture sensitive data (for example, an Ethernet device could see the contents of

packets that aren’t encrypted).

Whenever possible, Apple works to reduce the number of peripheral processors necessary

and to avoid designs that require firmware. But when separate processors with their own

firmware are required, efforts are taken to help ensure an attacker can’t persist on that

processor. This can be by verifying the processor in one of two ways:

• Running the processor so that it downloads verified firmware from the primary CPU on

startup

• Having the peripheral processor implement its own secure boot chain to verify the

peripheral processor firmware every time the Mac starts up

Apple works with vendors to audit their implementations and enhance their designs to

include desired properties such as:

• Ensuring minimum cryptographic strengths

• Ensuring strong revocation of known bad firmware

• Disabling debug interfaces

• Signing the firmware with cryptographic keys that are stored in Apple-controlled

hardware security modules (HSMs)

In recent years, Apple has worked with some external vendors to adopt the same “Image4”

data structures, verification code and signing infrastructure used by Apple silicon.

When neither storage-free operation nor storage plus secure boot is an option, the design

mandates that firmware updates be cryptographically signed and verified before the

persistent storage can be updated.

Rosetta 2 on a Mac with Apple silicon

A Mac with Apple silicon is capable of running code compiled for the x86_64 instruction

set using a translation mechanism called Rosetta 2. There are two types of translation

offered: just in time and ahead of time.

Just-in-time translation

In the just-in-time (JIT) translation pipeline, an x86_64 Mach object is identified early in

the image execution path. When these images are encountered, the kernel transfers control

to a special Rosetta translation stub rather than to the dynamic link editor, dyld(1).

The translation stub then translates x86_64 pages during the image’s execution. This

translation takes place entirely within the process. The kernel still verifies the code hashes

of each x86_64 page against the code signature attached to the binary as the page is

faulted in. In the event of a hash mismatch, the kernel enforces the remediation policy

appropriate for that process.

61Apple Platform Security

Ahead-of-time translation

In the ahead-of-time (AOT) translation path, x86_64 binaries are read from storage at

times the system deems optimal for responsiveness of that code. The translated artefacts

are written to storage as a special type of Mach object file. That file is similar to an

executable image, but it’s marked to indicate it’s the translated product of another image.

In this model, the AOT artefact derives all of its identity information from the original

x86_64 executable image. To enforce this binding, a privileged userspace entity signs the

translation artefact using a device-specific key that’s managed by the Secure Enclave. This

key is released only to the privileged userspace entity, which is identified as such using

a restricted entitlement. The code directory created for the translation artefact includes

the code directory hash of the original x86_64 executable image. The signature on the

translation artefact itself is known as the supplemental signature.

The AOT pipeline begins similarly to the JIT pipeline, with the kernel transferring control

to the Rosetta runtime rather than to the dynamic link editor, dyld(1). But the Rosetta

runtime then sends an inter-process communication (IPC) query to the Rosetta system

service, which asks whether there’s an AOT translation available for the current executable

image. If found, the Rosetta service provides a handle to that translation and it’s mapped

into the process and executed. During execution, the kernel enforces the code directory

hashes of the translation artefact which are authenticated by the signature rooted in the

device-specific signing key. The original x86_64 image’s code directory hashes aren’t

involved in this process.

Translated artefacts are stored in a Data Vault which isn’t running time-accessible by any

entity except for the Rosetta service. The Rosetta service manages access to its cache by

distributing read-only file descriptors to individual translation artefacts; this limits access

to the AOT artefact cache. This service’s inter-process communication and dependent

footprint are kept intentionally very narrow to limit its attack surface.

If the code directory hash of the original x86_64 image doesn’t match with the one

encoded into the AOT translation artefact’s signature, this result is considered the

equivalent of an invalid code signature, and appropriate enforcement action is taken.

If a remote process queries the kernel for the entitlements or other code identity properties

of an AOT-translated executable, the identity properties of the original x86_64 image are

returned to it.

Static trust cache content

macOS11 or later ships with Mach “fat” binaries that contain slices of x86_64 and arm64

computer code. On a Mac with Apple silicon, the user may decide to execute the x86_64

slice of a system binary through the Rosetta pipeline — for example, to load a plug-in that

has no native arm64 variant. To support this approach, the static trust cache that ships

with macOS generally contains three code directory hashes per Mach object file:

• A code directory hash of the arm64 slice

• A code directory hash of the x86_64 slice

• A code directory hash of the AOT translation of the x86_64 slice

62Apple Platform Security

The Rosetta AOT translation procedure is deterministic in that it reproduces identical

output for any given input, irrespective of when the translation was performed or on what

device it was performed.

During the macOS build, every Mach object file is run through the Rosetta AOT translation

pipeline associated with the version of macOS being built and the resulting code directory

hash is recorded into the trust cache. For efficiency, the actual translated products

don’t ship with the operating system and are reconstituted on demand when the user

requests them.

When an x86_64 image is being executed on a Mac with Apple silicon, if that image’s code

directory hash is in the static trust cache, the resulting AOT artefact’s code directory hash

is also expected to be in the static trust cache. Such products aren’t signed by the device-

specific key because the signing authority is rooted in the Apple secure boot chain.

Unsigned x86_64 code

A Mac with Apple silicon doesn’t permit native arm64 code to execute unless a valid

signature is attached. This signature can be as simple as an ad hoc code signature

(cf.codesign(1)) that doesn’t bear any actual identity from the secret half of an

asymmetric key pair (it’s simply an unauthenticated measurement of the binary).

For binary compatibility, translated x86_64 code is permitted to execute through Rosetta

with no signature information at all. No specific identity is conveyed to this code through

the device-specific Secure Enclave signing procedure, and it executes with precisely the

same limitations as native unsigned code executing on an Intel-based Mac.

Direct memory access protections for Mac computers

To achieve high throughput on high-speed interfaces like PCIe, FireWire, Thunderbolt and

USB, computers must support direct memory access (DMA) from peripherals. That is, they

must be able to read and write to RAM without continuous involvement of the CPU. Since

2012, Mac computers have implemented numerous technologies to protect DMA, resulting

in the best and most comprehensive set of DMA protections on any PC.

Direct memory access protections for a Mac with Apple silicon

Apple systems on chip contain an Input/Output Memory Management Unit (IOMMU) for

each DMA agent in the system, including PCIe and Thunderbolt ports. Because each

IOMMU has its own set of address translation tables to translate DMA requests, peripherals

connected by PCIe or Thunderbolt can access only memory that has been explicitly

mapped for their use. Peripherals can’t access memory belonging to other parts of the

system — such as the kernel or firmware memory assigned to other peripherals. If an

IOMMU detects an attempt by a peripheral to access memory that isn’t mapped for that

peripheral’s use, it triggers a kernel panic.

63Apple Platform Security

Direct memory access protections for an Intel-based Mac

Intel-based Mac computers with Intel Virtualization Technology for Directed I/O (VT-d)

initialise the IOMMU, enabling DMA remapping and interrupt remapping very early in the

boot process to mitigate various classes of security vulnerabilities. The Apple IOMMU

hardware begins operation with a default-deny policy, so the instant the system is powered

on, it automatically begins blocking DMA requests from peripherals. After being initialised

by software, the IOMMUs begin allowing DMA requests from peripherals to memory regions

that have been explicitly mapped for their use.

Note: Interrupt remapping for PCIe isn’t necessary on a Mac with Apple silicon because

each IOMMU handles MSIs for its own peripherals.

Starting in macOS 11, all Mac computers with an Apple T2 Security Chip run UEFI drivers

that facilitate DMA in a restricted ring 3 environment when these drivers are pairing with

external devices. This property helps mitigate security vulnerabilities that may occur

when a malicious device interacts with a UEFI driver in an unexpected way at boot time.

Inparticular, it reduces the impact of vulnerabilities in a driver’s handling of DMA buffers.

Kernel extensions in macOS

Starting with macOS 11, if third-party kernel extensions (kexts) are enabled, they can’t

be loaded into the kernel on demand. Instead, they’re merged into an Auxiliary Kernel

Collection (AuxKC), which is loaded during the boot process. For a Mac with Apple silicon,

the measurement of the AuxKC is signed in to the LocalPolicy (for previous hardware, the

AuxKC resided on the data volume). Rebuilding the AuxKC requires the user’s approval and

restarting of the macOS to load the changes into the kernel, and it requires that the secure

boot be configured to Reduced Security.

Important: Kexts are no longer recommended for macOS. Kexts risk the integrity and

reliability of the operating system and Apple recommends users select solutions that don’t

require extending the kernel.

Kernel extensions in a Mac with Apple silicon

Kexts must be explicitly enabled for a Mac with Apple silicon by holding the power button

at startup to enter into One True Recovery (1TR) mode, then downgrading to Reduced

Security and ticking the box to enable kernel extensions. This action also requires entering

an administrator password to authorise the downgrade. The combination of the 1TR and

password requirement makes it difficult for software-only attackers starting from within

macOS to inject kexts into macOS, which they can then exploit to gain kernel privileges.

After a user authorises kexts to load, the above User-Approved Kernel Extension Loading

flow is used to authorise the installation of kexts. The authorisation used for the above

flow is also used to capture an SHA384 hash of the user-authorised kext list (UAKL) in the

LocalPolicy. The kernel management daemon (kmd) is then responsible for validating only

those kexts found in the UAKL for inclusion into the AuxKC.

• If System Integrity Protection (SIP) is enabled, the signature of each kext is verified

before being included in the AuxKC.

• If SIP is disabled, the kext signature isn’t enforced.

This approach allows Permissive Security flows for developers or users who aren’t part of

the Apple Developer Programme to test kexts before they are signed.

64Apple Platform Security

After the AuxKC is created, its measurement is sent to the Secure Enclave to be signed

and included in an Image4 data structure that can be evaluated by iBoot at startup. As part

of the AuxKC construction, a kext receipt is also generated. This receipt contains the list

of kexts that were actually included in the AuxKC, because the set could be a subset of

the UAKL if banned kexts were encountered. An SHA384 hash of the AuxKC Image4 data

structure and the kext receipt are included in the LocalPolicy. The AuxKC Image4 hash is

used for extra verification by iBoot at startup to help ensure that it isn’t possible to start

up an older Secure Enclave–signed AuxKC Image4 file with a newer LocalPolicy. The kext

receipt is used by subsystems such as ApplePay to determine whether there are any kexts

currently loaded that could interfere with the trustworthiness of macOS. If there are, then

ApplePay capabilities may be disabled.

Alternatives to kexts (macOS 10.15 or later)

macOS 10.15 allows developers to extend the capabilities of macOS by installing and

managing system extensions that run in user space rather than at the kernel level. By

running in user space, system extensions increase the stability and security of macOS. Even

though kexts inherently have full access to the entire operating system, extensions running

in user space are granted only the privileges necessary to perform their specified function.

Developers can use frameworks, including DriverKit, EndpointSecurity and NetworkExtension,

to write USB and human interface drivers, endpoint security tools (like data loss prevention

or other endpoint agents), and VPN and network tools, all without needing to write kexts.

Third-party security agents should be used only if they take advantage of these APIs or

have a robust road map to transition to them and away from kernel extensions.

User-Approved Kernel Extension Loading

To improve security, user consent is required to load kernel extensions installed with or

after installing macOS 10.13. This process is known as User-Approved Kernel Extension

Loading. Administrator authorisation is required to approve a kernel extension. Kernel

extensions don’t require authorisation if they:

• Were installed on a Mac when using macOS 10.12 or earlier

• Are replacing previously approved extensions

• Are allowed to load without user consent by using the spctl command-line tool

available when a Mac was booted from recoveryOS

• Are allowed to load using mobile device management (MDM) configuration

Starting with macOS 10.13.2, users can use MDM to specify a list of kernel extensions

that load without user consent. This option requires a Mac with macOS 10.13.2 that’s

enrolled in MDM — through Apple School Manager, Apple Business Manager or MDM

enrolment done by the user.

65Apple Platform Security

Option ROM security in macOS

Note: Option ROMs aren’t currently supported on a Mac with Apple silicon.

Option ROM security in a Mac with the Apple T2 Security Chip

Both Thunderbolt and PCIe devices can have an “Option ROM (OROM)” physically attached

to the device. (This is typically not a true ROM but is instead a rewritable chip that stores

firmware.) On UEFI-based systems, that firmware is typically a UEFI driver which is read

in by the UEFI firmware and executed. The executed code is supposed to initialise and

configure the hardware it was retrieved from, so that the hardware can be made usable by

the rest of the firmware. This capability is required so that specialised third-party hardware

can load and operate during the earliest startup phases — for example, to start up from

external RAID arrays.

However, because OROMs are generally rewritable, if an attacker overwrites the OROM of a

legitimate peripheral, the attacker’s code executes early in the boot process and is able to

tamper with the execution environment and violate the integrity of software that’s loaded

later. Likewise, if the attacker introduces their own malicious device to the system, they’re

also able to execute malicious code.

In macOS 10.12.3, the behaviour of Mac computers sold after 2011 was changed to not

execute OROMs by default at the time the Mac booted unless a special key combination

was pressed. This key combination protected against malicious OROMs being inadvertently

introduced into the macOS boot sequence. The default behaviour of the Firmware

Password Utility was also changed so that when the user set a firmware password, OROMs

couldn’t execute even if the key combination was pressed. This protected against a

physically present attacker intentionally introducing a malicious OROM. For users who still

need to run OROMs while they have a firmware password set, a non-default option can be

configured using the firmwarepasswd command-line tool in macOS.

66Apple Platform Security

OROM sandbox security

In macOS 10.15, UEFI firmware was updated to contain a mechanism for sandboxing

OROMs and for stripping privileges from them. UEFI firmware typically executes all code,

including OROMs, at the maximum CPU privilege level, called ring 0, and has a single

shared virtual memory space for all code and data. Ring 0 is the privilege level where the

macOS kernel runs, whereas the lower privilege level, ring 3, is where apps run. The OROM

sandbox de-privileged OROMs by making use of virtual memory separation like the kernel

does and then making the OROMs run in ring 3.

The sandbox further significantly restricts both the interfaces that the OROMs can call

(much like system call filtering in kernels) and the type of device that an OROM can

can no longer directly write anywhere within ring 0 memory. Instead, they are limited to a

very narrow and well-defined sandbox interface. This limited interface significantly reduces

attack surface and forces attackers to first escape the sandbox and escalate privilege.

67Apple Platform Security

UEFI firmware security in an Intel-based Mac

An Intel-based Mac with an Apple T2 Security Chip offers security using UEFI (Intel) firmware.

Overview

Since 2006, Mac computers with an Intel-based CPU use an Intel firmware based on the

Extensible Firmware Interface (EFI) Development Kit (EDK) version 1 or version 2. EDK2-

based code conforms to the Unified Extensible Firmware Interface (UEFI) specification.

This section refers to the Intel firmware as the UEFI firmware. The UEFI firmware was the

first code to execute on the Intel chip.

For an Intel-based Mac without the Apple T2 Security Chip, the root of trust for the UEFI

firmware is the chip where the firmware is stored. UEFI firmware updates are digitally

signed by Apple and verified by the firmware before updating the storage. To help prevent

rollback attacks, updates must always have a version newer than the existing one. However,

an attacker with physical access to the Mac could potentially use hardware to attach to

the firmware storage chip and update the chip to contain malicious content. Likewise,

ifvulnerabilities are found in the early boot process of the UEFI firmware (before it write-

restricts the storage chip), this could also lead to persistent infection of the UEFI firmware.

This is a hardware architectural limitation common in most Intel-based PCs and present in

all Intel-based Mac computers without the T2 chip.

To help prevent physical attacks that subvert UEFI firmware, Mac computers were

rearchitected to root the trust in the UEFI firmware in the T2 chip. On these Mac

computers, the root of trust for the UEFI firmware is specifically the T2 firmware, as

described in Boot process for an Intel-based Mac.

Intel Management Engine (ME) subcomponent

One subcomponent stored within the UEFI firmware is the Intel Management Engine (ME)

firmware. The ME — a separate processor and subsystem within Intel chips — is used

primarily for audio and video copyright protection on a Mac that has only Intel-based

graphics. To reduce this subcomponent’s attack surface, an Intel-based Mac runs a custom

ME firmware from which most components have been removed. Because the resulting

Mac ME firmware is smaller than the default minimal build that Intel makes available, many

components that have been the subject of public attacks by security researchers in the

past are no longer present.

System Management Mode (SMM)

Intel processors have a special execution mode that’s distinct from normal operation.

Called System Management Mode (SMM), it was originally introduced to handle time-

sensitive operations such as power management. However, to perform such actions, Mac

computers have historically used a discrete microcontroller called the System Management

Controller (SMC). No longer a separate microcontroller, the SMC has been integrated into

the T2 chip.

68Apple Platform Security

System security for watchOS

AppleWatch uses many of the same hardware-based platform security capabilities that

iOS and iPadOS use. For example, AppleWatch:

• Performs secure boot and secure software updates

• Maintains operating system integrity

• Helps protect data — both on the device and when communicating with a paired iPhone

or the internet

Supported technologies include those listed in System Security (for example, KIP, SKP and

SCIP) as well as Data Protection, keychain and network technologies.

Updating watchOS

watchOS can be configured to update overnight. For more information on how the

AppleWatch passcode gets stored and used during the update, see Keybags.

Wrist detection

If wrist detection is enabled, the device locks automatically soon after it’s removed from

the user’s wrist. If wrist detection is disabled, Control Centre provides an option for locking

AppleWatch. When AppleWatch is locked, ApplePay can be used only by entering the

passcode on the AppleWatch. Wrist detection is turned off using the AppleWatch app on

iPhone. This setting can also be enforced using a mobile device management (MDM) solution.

Activation Lock

When Find My is turned on on iPhone, its paired AppleWatch can use Activation Lock.

Activation Lock makes it harder for anyone to use or sell an AppleWatch that’s been lost

or stolen. Activation Lock requires the user’s AppleID and password to unpair, erase or

reactivate an AppleWatch.

Secure pairing with iPhone

AppleWatch can be paired with only one iPhone at a time. When AppleWatch is unpaired,

iPhone communicates instructions to erase all content and data from the watch.

Pairing AppleWatch with iPhone is secured using an out-of-band process to exchange

public keys, followed by the Bluetooth Low Energy (BLE) link shared secret. AppleWatch

displays an animated pattern which is captured by the camera on iPhone. The pattern

contains an encoded secret that’s used for BLE 4.1 out-of-band pairing. Standard BLE

Passkey Entry is used as a fallback pairing method, if necessary.

After the BLE session is established and encrypted using the highest security protocol available

in the Bluetooth Core Specification, iPhone and AppleWatch exchange keys using either:

• A process adapted from AppleIDentity Service (IDS) as described in the iMessage

security overview.

• A key exchange using IKEv2/IPsec. The initial key exchange is authenticated using either

the Bluetooth session key (for pairing scenarios) or the IDS keys (for operating system

update scenarios). Each device generates a random public and private 256-bit Ed25519

key pair and, during the initial key exchange process, the public keys are exchanged.

69Apple Platform Security

Note: The mechanism used for key exchange and encryption varies, depending on

which operating system versions are on the iPhone and AppleWatch. iPhone devices

with iOS13 or later when paired with an AppleWatch with watchOS6 or later use only

IKEv2/IPsec for key exchange and encryption.

After keys have been exchanged:

• The Bluetooth session key is discarded and all communications between iPhone and

AppleWatch are encrypted using one of the methods listed above — with the encrypted

Bluetooth, Wi-Fi and mobile data links providing a secondary encryption layer.

• (IKEv2/IPsec only) The keys are stored in the System keychain and used for

authenticating future IKEv2/IPsec sessions between the devices. Further communication

between these devices is encrypted and integrity protected using AES-256-GCM or

ChaCha20-Poly1305 (256-bit keys) on iPhone devices using iOS15 or later paired with

an AppleWatch Series 4 or later using watchOS8 or later.

The Bluetooth Low Energy device address is rotated at 15-minute intervals to reduce the

risk of the device being locally tracked if someone broadcasts a persistent identifier.

To support apps that need streaming data, encryption is provided with methods described

in FaceTime security using either the AppleIDentity Service (IDS) provided by the paired

iPhone or a direct internet connection.

AppleWatch implements hardware-encrypted storage and class-based protection of files

and keychain items. Access-controlled keybags for keychain items are also used. Keys

used to communicate between AppleWatch and iPhone are also secured using class-based

protection. For more information, see Keybags for Data Protection.

Auto Unlock and AppleWatch

For greater convenience when using multiple Apple devices, some devices can

automatically unlock others in certain situations. Auto Unlock supports three uses:

• An AppleWatch can be unlocked by an iPhone.

• A Mac can be unlocked by an AppleWatch.

• An iPhone can be unlocked by an AppleWatch when a user is detected with their nose

and mouth covered.

All three use cases are built upon the same basic foundation: a mutually authenticated

Station-to-Station (STS) protocol, with Long-Term Keys exchanged at time of feature

enablement and unique ephemeral session keys negotiated for each request. Regardless of

the underlying communication channel, the STS tunnel is negotiated directly between the

Secure Enclaves in both devices, and all cryptographic material is kept within that secure

domain (with the exception of Mac computers without a Secure Enclave, which terminate

the STS tunnel in the kernel).

Unlocking

A complete unlock sequence can be broken down into two phases. First, the device being

unlocked (the “target”) generates a cryptographic unlock secret and sends it to the device

performing the unlock (the “initiator”). Later, the initiator performs the unlock using the

previously generated secret.

70Apple Platform Security

To arm auto unlock, the devices connect to each other using a BLE connection. Then a

32-byte unlock secret randomly generated by the target device is sent to the initiator over

the STS tunnel. During the next biometric or passcode unlock, the target device wraps its

passcode-derived key (PDK) with the unlock secret and discards the unlock secret from its

memory.

To perform the unlock, the devices initiate a new BLE connection and then use peer-to-

peer Wi-Fi to securely approximate the distance between each other. If the devices are

within the specified range and the required security policies are met, the initiator sends

its unlock secret to the target through the STS tunnel. The target then generates a new

32-byte unlock secret and returns it to the initiator. If the current unlock secret sent by the

initiator successfully decrypts the unlock record, the target device is unlocked and the PDK

is rewrapped with a new unlock secret. Finally, the new unlock secret and PDK are then

discarded from the target’s memory.

AppleWatch Auto Unlock security policies

For added convenience, AppleWatch can be unlocked by an iPhone directly after initial

startup, without requiring the user to first enter the passcode on the AppleWatch itself.

Toachieve this, the random unlock secret (generated during the very first unlock sequence

after enablement of the feature) is used to create a long-term escrow record, which

is stored in the AppleWatch keybag. The escrow record secret is stored in the iPhone

keychain and used to bootstrap a new session after each AppleWatch restart.

iPhone Auto Unlock security policies

Additional security policies apply to iPhone Auto Unlock with AppleWatch. AppleWatch

can’t be used in place of FaceID on iPhone for other operations, such as ApplePay or

app authorisations. When AppleWatch successfully unlocks a paired iPhone, the watch

displays a notification and plays an associated haptic. If the user taps the Lock iPhone

button in the notification, the watch sends the iPhone a lock command over BLE. When the

iPhone receives the lock command, it locks and disables both FaceID and unlock using

AppleWatch. The next iPhone unlock must be performed with the iPhone passcode.

Successfully unlocking a paired iPhone from AppleWatch (when enabled) requires the

following criteria be met:

• iPhone must have been unlocked using another method at least once after the

associated AppleWatch was placed on wrist and unlocked.

• Sensors must be able to detect that the nose and mouth are covered.

• Distance measured must be 2–3 metres or less

• AppleWatch must not be in Bedtime mode.

• AppleWatch or iPhone must have been unlocked recently, or AppleWatch must have

experienced physical motion indicating that the wearer is active (for example, not asleep).

• iPhone must have been unlocked at least once in the past 6.5 hours.

• iPhone must be in a state where FaceID is allowed to perform a device unlock.

(Formore information, see FaceID, TouchID, passcodes and passwords.)

71Apple Platform Security

Approve in macOS with AppleWatch

When Auto Unlock with AppleWatch is enabled, the AppleWatch can be used in place, or

together with TouchID, to approve authorisation and authentication prompts from:

• macOS and Apple apps that request authorisation

• Third-party apps that request authentication

• Saved Safari passwords

• Secure Notes

Secure use of Wi-Fi, mobile, iCloud and Gmail

When AppleWatch isn’t within Bluetooth range, Wi-Fi or mobile data can be used instead.

AppleWatch automatically joins Wi-Fi networks that have already been joined on the paired

iPhone and whose credentials have synced to the AppleWatch while both devices were

in range. This Auto-Join behaviour can then be configured on a per-network basis in the

Wi-Fi section of the AppleWatch Settings app. Wi-Fi networks that have never been joined

before on either device can be manually joined in the Wi-Fi section of the AppleWatch

Settings app.

When AppleWatch and iPhone are out of range, AppleWatch connects directly to iCloud

and Gmail servers to fetch Mail, as opposed to syncing Mail data with the paired iPhone

over the internet. For Gmail accounts, the user must authenticate to Google in the Mail

section of the Watch app on iPhone. The OAuth token received from Google is sent over to

AppleWatch in encrypted format over AppleIDentity Service (IDS) so that it can be used to

fetch Mail. This OAuth token is never used for connectivity with the Gmail server from the

paired iPhone.

Random number generation

Cryptographic pseudo-random number generators (CPRNGs) are an important building

block for secure software. To this end, Apple provides a trusted software CPRNG running

in the iOS, iPadOS, macOS, tvOS and watchOS kernels. It’s responsible for aggregating raw

entropy from the system and providing secure random numbers to consumers in both the

kernel and user space.

Entropy sources

The kernel CPRNG is seeded from multiple entropy sources during boot and over the

lifetime of the device. These include (contingent on availability):

• The Secure Enclave hardware TRNG

• Timing-based jitter collected during boot

• Entropy collected from hardware interrupts

• A seed file used to persist entropy across boots

• Intel random instructions — for example, RDSEED and RDRAND (only on an Intel-based Mac)

72Apple Platform Security

The kernel CPRNG

The kernel CPRNG is a Fortuna-derived design targeting a 256-bit security level. It

provides high-quality random numbers to user-space consumers using the following APIs:

• The getentropy(2) system call

• The random device (/dev/random)

The kernel CPRNG accepts user-supplied entropy through writes to the random device.

Apple Security Research Device

The Apple Security Research Device is a specially fused iPhone that allows security

researchers to perform research on iOS without having to defeat or disable the platform

security features of iPhone. With this device, a researcher can side-load content that runs

with platform-equivalent permissions and thus perform research on a platform that more

closely models that of production devices.

To help ensure that user devices aren’t affected by the security research device execution

policy, the policy changes are implemented in a variant of iBoot and in the Boot Kernel

Collection. These fail to boot on user hardware. The research iBoot checks for a new fusing

state and enters a panic loop if it’s being run on non-research-fused hardware.

The cryptex subsystem allows a researcher to load a personalised trust cache and a disk

image containing corresponding content. A number of in-depth defence measures have

been implemented that are designed to ensure that this subsystem doesn’t allow execution

on user devices:

• launchd doesn’t load the cryptexd launchd property list if it detects a normal

customer device.

• cryptexd aborts if it detects a normal customer device.

• AppleImage4 doesn’t vend the nonce used for verifying a research cryptex on a normal

customer device.

• The signing server refuses to personalise a cryptex disk image for a device not on an

explicit allow list.

To respect the privacy of the security researcher, only the measurements (for example,

hashes) of the executables or kernel cache and the security research device identifiers

are sent to Apple during personalisation. Apple doesn’t receive the content of the cryptex

being loaded onto the device.

73Apple Platform Security

To avoid having a malicious party attempt to masquerade a research device as a user

device to trick a target into using it for everyday usage, the security research device has

the following differences:

• The security research device starts up only while charging. This can be using a

Lightning cable or a Qi-compatible charger. If the device isn’t charging during startup,

the device enters Recovery mode. If the user starts charging and restarts the device, it

starts up as normal. As soon as XNU starts, the device doesn’t need to be charging to

continue operation.

• The words Security Research Device are displayed below the Apple logo during iBoot

startup.

• The XNU kernel boots in verbose mode.

• The device is etched on the side with the message “Property of Apple. Confidential and

Proprietary. Call +1 877 595 1125”.

The following are additional measures that are implemented in software that appears

after boot:

• The words Security Research Device are displayed during device setup.

• The words Security Research Device are displayed on the Lock Screen and in the

Settings app.

The Security Research Device affords researchers the following abilities that a user device

doesn’t. Researchers can:

• Side-load executable code onto the device with arbitrary entitlements at the same

permission level as Apple operating system components

• Start services at startup

• Persist content across restarts

• Use the research.com.apple.license-to-operate entitlement to permit a process

to debug any other process on the system, including system processes.

The research. namespace is respected only by the RESEARCH variant of the

AppleMobileFileIntegrity kernel extension; any process with this entitlement is

terminated on a customer device during signature validation.

• Personalise and restore a custom kernel cache

74Apple Platform Security

Encryption and Data Protection

Encryption and Data Protection overview

The secure boot chain, system security and app security capabilities all help to verify that

only trusted code and apps run on a device. Apple devices have additional encryption

features to safeguard user data even when other parts of the security infrastructure have

been compromised (for example, if a device is lost or is running untrusted code). All these

features benefit both users and IT administrators, protecting personal and corporate

information and providing methods for instant and complete remote wipe in the case of

device theft or loss.

iOS and iPadOS devices use a file encryption methodology called Data Protection, whereas

the data on an Intel-based Mac is protected with a volume encryption technology called

FileVault. A Mac with Apple silicon uses a hybrid model that supports Data Protection,

with two caveats: The lowest protection level (Class D) isn’t supported, and the default

level (Class C) uses a volume key and acts just like the FileVault on an Intel-based Mac. In

all cases, key management hierarchies are rooted in the dedicated silicon of the Secure

Enclave, and a dedicated AES Engine supports line-speed encryption and helps ensure that

long-lived encryption keys aren’t exposed to the kernel operating system or CPU (where

they might be compromised). (An Intel-based Mac with a T1 or lacking a Secure Enclave

doesn’t use dedicated silicon to protect its FileVault encryption keys.)

Besides using Data Protection and FileVault to help prevent unauthorised access to data,

Apple uses operating system kernels to enforce protection and security. The kernel uses

access controls to sandbox apps (which restricts what data an app can access) and a

mechanism called a Data Vault (which rather than restricting the calls an app can make,

restricts access to the data of an app from all other requesting apps).

Passcodes and passwords

To protect user data from malicious attack, Apple uses passcodes in iOS and iPadOS

and passwords in macOS. The longer a passcode or password is, the stronger it is — and

the easier it is to discourage brute-force attacks. To further discourage attacks, Apple

enforces time delays (for iOS and iPadOS) and a limited number of password attempts

(for Mac).

In iOS and iPadOS, when setting up a device passcode or password, the user automatically

enables Data Protection. Data Protection is also enabled on other devices that feature

an Apple system on chip (SoC) — such as a Mac with Apple silicon, AppleTV and

AppleWatch. In macOS, Apple uses the built-in volume encryption program FileVault.

75Apple Platform Security

How strong passcodes and passwords increase security

iOS and iPadOS support six-digit, four-digit and arbitrary-length alphanumeric passcodes.

Besides unlocking the device, a passcode or password provides entropy for certain

encryption keys. This means an attacker in possession of a device can’t get access to data

in specific protection classes without the passcode.

The passcode or password is entangled with the device’s UID, so brute-force attempts

must be performed on the device under attack. A large iteration count is used to make each

attempt slower. The iteration count is calibrated so that one attempt takes approximately 80

milliseconds. In fact, it would take more than five and a half years to try all combinations of a

six-character alphanumeric passcode with lowercase letters and numbers.

The stronger the user passcode is, the stronger the encryption key becomes. And by

using FaceID and TouchID, the user can establish a much stronger passcode than would

otherwise be practical. The stronger passcode increases the effective amount of entropy

protecting the encryption keys used for Data Protection, without adversely affecting the

user experience of unlocking a device multiple times throughout the day.

If a long password that contains only numbers is entered, a numeric keypad is displayed at

the Lock Screen instead of the full keyboard. A longer numeric passcode may be easier to

enter than a shorter alphanumeric passcode, while providing similar security.

Users can specify a longer alphanumeric passcode by selecting Custom Alphanumeric

Code in the Passcode Options in Settings > TouchID & Passcode or FaceID & Passcode.

How escalating time delays discourage brute-force attacks

(iOS, iPadOS)

In iOS and iPadOS, to further discourage brute-force passcode attacks, there are

escalating time delays after the entry of an invalid passcode at the Lock Screen, as shown

in the table below.

Attempts Delay enforced

1–4 None

51 minute

65 minutes

7–8 15 minutes

91 hour

If the Erase Data option is turned on (in Settings > TouchID & Passcode), after 10

consecutive incorrect attempts to enter the passcode, all content and settings are removed

from storage. Consecutive attempts of the same incorrect passcode don’t count towards

the limit. This setting is also available as an administrative policy through a mobile device

management (MDM) solution that supports this feature and through Microsoft Exchange

ActiveSync, and can be set to a lower threshold.

On devices with Secure Enclave, the delays are enforced by the Secure Enclave. If the

device is restarted during a timed delay, the delay is still enforced, with the timer starting

again for the current period.

76Apple Platform Security

How escalating time delays discourage brute-force attacks

(macOS)

To help prevent brute-force attacks, when Mac starts up, no more than 10 password

attempts are allowed at the Login Window or using Target Disk Mode, and escalating time

delays are imposed after a certain number of incorrect attempts. The delays are enforced

by the Secure Enclave. If Mac is restarted during a timed delay, the delay is still enforced,

with the timer starting again for the current period.

The table below shows delays between password attempts on a Mac with Apple silicon and

a Mac with a T2 chip.

Attempts Delay enforced

51 minute

65 minutes

715 minutes

815 minutes

91 hour

10 Disabled

To help prevent malware from causing permanent data loss by trying to attack the user’s

password, these limits aren’t enforced after the user has successfully logged in to the Mac,

but they are reimposed after reboot. If the 10 attempts are exhausted, 10 more attempts

are available after booting into recoveryOS. And if those are also exhausted, then 10

additional attempts are available for each FileVault recovery mechanism (iCloud recovery,

FileVault recovery key and institutional key), for a maximum of 30 additional attempts.

After those additional attempts are exhausted, the Secure Enclave no longer processes any

requests to decrypt the volume or verify the password and the data on the drive becomes

unrecoverable.

To help protect data in an enterprise setting, IT should define and enforce FileVault

configuration policies using an MDM solution. Organisations have several options for

managing encrypted volumes, including institutional recovery keys, personal recovery keys

(that can optionally be stored with MDM for escrow) or a combination of both. Key rotation

can also be set as a policy in MDM.

On a Mac with the Apple T2 Security Chip, the password serves a similar function except

that the key generated is used for FileVault encryption rather than Data Protection. macOS

also offers additional password recovery options:

• iCloud recovery

• FileVault recovery

• FileVault institutional key

77Apple Platform Security

Data Protection

Data Protection overview

Apple uses a technology called Data Protection to protect data stored in flash storage on

the devices that feature an Apple SoC — such as iPhone, iPad, AppleWatch, AppleTV and

a Mac with Apple silicon. With Data Protection, a device can respond to common events,

such as incoming phone calls, while at the same time providing a high level of encryption

for user data. Certain system apps (such as Messages, Mail, Calendar, Contacts, Photos)

and Health data values use Data Protection by default. Third-party apps receive this

protection automatically.

Implementation

Data Protection is implemented by constructing and managing a hierarchy of keys and

builds on the hardware encryption technologies built into Apple devices. Data Protection is

controlled on a per-file basis by assigning each file to a class; accessibility is determined

according to whether the class keys have been unlocked. APFS (Apple File System) allows

the file system to further subdivide the keys into a per-extent basis (where portions of a

file can have different keys).

Every time a file on the data volume is created, Data Protection creates a new 256-bit key

(the per-file key) and gives it to the hardware AES Engine, which uses the key to encrypt

the file as it’s written to flash storage. On A14, A15 and M1 family devices, the encryption

uses AES-256 in XTS mode, where the 256-bit per-file key goes through a Key Derivation

Function (NIST Special Publication 800-108) to derive a 256-bit tweak and a 256-bit

cipher key. The hardware generations of A9 to A13, S5, S6 and S7 use AES-128 in XTS

mode, where the 256-bit per-file key is split to provide a 128-bit tweak and a 128-bit

cipher key.

On a Mac with Apple silicon, Data Protection defaults to Class C (see Data Protection

classes) but utilises a volume key rather than a per-extent or per-file key — effectively

recreating the security model of FileVault for user data. Users must still opt in to FileVault

to receive the full protection of entangling the encryption key hierarchy with their

password. Developers can also opt in to a higher protection class that uses a per-file or

per-extent key.

Data Protection in Apple devices

On Apple devices with Data Protection, each file is protected with a unique per-file (or per-

extent) key. The key, wrapped using the NIST AED key wrap algorithm, is further wrapped

with one of several class keys, depending on how the file is meant to be accessed. The

wrapped per-file key is then stored in the file’s metadata.

Devices with APFS format may support cloning of files (zero-cost copies using copy-

on-write technology). If a file is cloned, each half of the clone gets a new key to accept

incoming writes so that new data is written to the media with a new key. Over time, the file

may become composed of various extents (or fragments), each mapping to different keys.

However, all the extents that comprise a file are guarded by the same class key.

78Apple Platform Security

When a file is opened, its metadata is decrypted with the file system key, revealing the

wrapped per-file key and a notation on which class protects it. The per-file (or per-extent)

key is unwrapped with the class key and then supplied to the hardware AES Engine, which

decrypts the file as it’s read from flash storage. All wrapped file key handling occurs in

the Secure Enclave; the file key is never directly exposed to the Application Processor. At

startup, the Secure Enclave negotiates an ephemeral key with the AES Engine. When the

Secure Enclave unwraps a file’s keys, they’re rewrapped with the ephemeral key and sent

back to the Application Processor.

The metadata of all files in the data volume file system are encrypted with a random

volume key, which is created when the operating system is first installed or when the

device is wiped by a user. This key is encrypted and wrapped by a key-wrapping key that

is known only to the Secure Enclave for long-term storage. The key-wrapping key changes

every time a user erases their device. On A9 (and newer) SoCs, Secure Enclave relies upon

entropy, backed by anti-replay systems, to achieve effaceability and to protect its key

wrapping key, among other assets. For more information, see Secure non-volatile storage.

Just like per-file or per-extent keys, the metadata key of the data volume is never directly

exposed to the Application Processor; the Secure Enclave provides an ephemeral, per-boot

version instead. When stored, the encrypted file system key is additionally wrapped by an

“effaceable key” stored in Effaceable Storage or using a media key-wrapping key, protected

by Secure Enclave anti-replay mechanism. This key doesn’t provide additional confidentiality

of data. Instead, it’s designed to be quickly erased on demand (by the user with the “Erase

All Content and Settings” option, or by a user or administrator issuing a remote wipe

command from a mobile device management (MDM) solution, Microsoft Exchange ActiveSync

or iCloud). Erasing the key in this manner renders all files cryptographically inaccessible.

The contents of a file may be encrypted with one or more per-file (or per-extent) keys that

are wrapped with a class key and stored in a file’s metadata, which in turn is encrypted

with the file system key. The class key is protected with the hardware UID and, for some

classes, the user’s passcode. This hierarchy provides both flexibility and performance. For

example, changing a file’s class only requires rewrapping its per-file key and a change of

passcode just rewraps the class key.

Data Protection classes

When a new file is created on devices supporting Data Protection, it’s assigned a class

by the app that creates it. Each class uses different policies to determine when the data

is accessible. The basic classes and policies are described in the following sections.

Apple silicon–based Mac computers don’t support Class D: No Protection, and a security

boundary is established around logging in and out (not locking or unlocking as on iPhone,

iPad and iPodtouch).

Class Protection type

Class A: Complete Protection NSFile Protection Complete

Class B: Protected Unless Open NSFile Protection Complete Unless Open

Class C: Protected Until First User Authentication

Note: macOS uses a volume key to recreate File Vault

protection characteristics.

NSFile Protection Complete Until First User Authentication

Class D: No Protection

Note: Not supported in macOS.

NSFile Protection None

79Apple Platform Security

Complete Protection

NSFileProtectionComplete: The class key is protected with a key derived from the

user passcode or password and the device UID. Shortly after the user locks a device

(10seconds, if the Require Password setting is Immediately), the decrypted class key is

discarded, rendering all data in this class inaccessible until the user enters the passcode

again or unlocks (logs in to) the device using FaceID or TouchID.

In macOS, shortly after the last user is logged out, the decrypted class key is discarded,

rendering all data in this class inaccessible until a user enters the passcode again or logs in

to the device using TouchID.

Protected Unless Open

NSFileProtectionCompleteUnlessOpen: Some files may need to be written while the

device is locked or the user is logged out. A good example of this is a mail attachment

downloading in the background. This behaviour is achieved by using asymmetric elliptic

curve cryptography (ECDH over Curve25519). The usual per-file key is protected by a key

derived using One-Pass Diffie-Hellman Key Agreement as described in NIST SP 800-56A.

The ephemeral public key for the Agreement is stored alongside the wrapped per-file key. The

KDF is Concatenation Key Derivation Function (Approved Alternative 1) as described in 5.8.1

of NIST SP 800-56A. AlgorithmID is omitted. PartyUInfo and PartyVInfo are the ephemeral and

static public keys, respectively. SHA256 is used as the hashing function. As soon as the file

is closed, the per-file key is wiped from memory. To open the file again, the shared secret is

re-created using the Protected Unless Open class’s private key and the file’s ephemeral public

key, which are used to unwrap the per-file key that is then used to decrypt the file.

In macOS, the private part of NSFileProtectionCompleteUnlessOpen is accessible as long

as any users on the system are logged in or are authenticated.

Protected Until First User Authentication

NSFileProtectionCompleteUntilFirstUserAuthentication: This class behaves in the same way

as Complete Protection, except that the decrypted class key isn’t removed from memory

when the device is locked or the user logged out. The protection in this class has similar

properties to desktop full-volume encryption and protects data from attacks that involve

a reboot. This is the default class for all third-party app data not otherwise assigned to a

Data Protection class.

In macOS, this class utilises a volume key that is accessible as long as the volume is

mounted, and acts just like FileVault.

No Protection

NSFileProtectionNone: This class key is protected only with the UID and is kept in Effaceable

Storage. Since all the keys needed to decrypt files in this class are stored on the device, the

encryption only affords the benefit of fast remote wipe. If a file isn’t assigned a Data Protection

class, it is still stored in encrypted form (as is all data on an iOS and iPadOS device).

This isn’t supported in macOS.

Note: In macOS, for volumes that don’t correspond to a booted operating system, all data

protection classes are accessible as long as the volume is mounted. The default data

protection class is NSFileProtectionCompleteUntilFirstUserAuthentication. Per-extent key

functionality is available to both Rosetta 2 and native apps.

80Apple Platform Security

Keybags for Data Protection

The keys for both file and keychain Data Protection classes are collected and managed in

keybags on iOS, iPadOS, watchOS and tvOS. These operating systems use the following

keybags: user, device, backup, escrow and iCloud Backup.

User keybag

The user keybag is where the wrapped class keys used in the normal operation of the

device are stored. For example, when a passcode is entered, NSFileProtectionComplete is

loaded from the user keybag and unwrapped. It is a binary property list (.plist) file stored in

the No Protection class.

For devices with SoCs earlier than the A9, the .plist file contents are encrypted with a

key held in Effaceable Storage. To give forward security to keybags, this key is wiped and

regenerated each time a user changes their passcode.

For devices with the A9 or later SoCs, the .plist file contains a key that indicates the

keybag is stored in a locker protected by the Secure Enclave–controlled anti-replay nonce.

The Secure Enclave manages the user keybag and can be queried regarding a device’s lock

state. It reports that the device is unlocked only if all the class keys in the user keybag are

accessible and have been unwrapped successfully.

Device keybag

The device keybag is used to store the wrapped class keys used for operations involving

device-specific data. iPadOS devices configured for shared use sometimes need access to

credentials before any user has logged in; therefore, a keybag that isn’t protected by the

user’s passcode is required.

iOS and iPadOS don’t support cryptographic separation of per-user file system content,

which means the system uses class keys from the device keybag to wrap per-file keys.

The keychain, however, uses class keys from the user keybag to protect items in the

user keychain. In iOS and iPadOS devices configured for use by a single user (the default

configuration), the device keybag and the user keybag are one and the same and are

protected by the user’s passcode.

Backup keybag

The backup keybag is created when an encrypted backup is made by the Finder (in macOS 10.15

or later) or iTunes (in macOS 10.14 or earlier) and stored on the computer to which the

device is backed up. A new keybag is created with a new set of keys, and the backed-up

data is re-encrypted to these new keys. As explained previously, non-migratory keychain

items remain wrapped with the UID-derived key, allowing them to be restored to the device

they were originally backed up from but rendering them inaccessible on a different device.

The keybag — protected with the password set — is run through 10 million iterations of

the key derivation function PBKDF2. Despite this large iteration count, there’s no tie to

a specific device and therefore a brute-force attack parallelised across many computers

could theoretically be attempted on the backup keybag. This threat can be mitigated with a

sufficiently strong password.

If a user chooses not to encrypt the backup, the files aren’t encrypted regardless of their

Data Protection class but the keychain remains protected with a UID-derived key. This is

why keychain items migrate to a new device only if a backup password is set.

81Apple Platform Security

Escrow keybag

The escrow keybag is used for syncing with the Finder (macOS 10.15 or later) or iTunes

(macOS 10.14 or earlier) through USB and mobile device management (MDM). This keybag

allows the Finder or iTunes to back up and sync without requiring the user to enter a

passcode, and it allows an MDM solution to remotely clear a user’s passcode. It is stored

on the computer that’s used to sync with the Finder or iTunes, or on the MDM solution that

remotely manages the device.

The escrow keybag improves the user experience during device syncing, which potentially

requires access to all classes of data. When a passcode-locked device is first connected

to the Finder or iTunes, the user is prompted to enter a passcode. The device then creates

an escrow keybag containing the same class keys used on the device, protected by a newly

generated key. The escrow keybag and the key protecting it are split between the device

and the host or server, with the data stored on the device in the Protected Until First User

Authentication class. This is why the device passcode must be entered before the user

backs up with the Finder or iTunes for the first time after a reboot.

In the case of an over-the-air (OTA) software update, the user is prompted for their

passcode when initiating the update. This is used to securely create a single-use unlock

token, which unlocks the user keybag after the update. This token can’t be generated

without entering the user’s passcode, and any previously generated token is invalidated if

the user’s passcode is changed.

Single-use unlock tokens are either for attended or unattended installation of a software

update. They’re encrypted with a key derived from the current value of a monotonic

counter in the Secure Enclave, the UUID of the keybag and the Secure Enclave UID.

On A9 (and later) SoCs, a single-use Unlock token no longer relies on counters or

Effaceable Storage. Instead, it’s protected by Secure Enclave controlled anti-replay nonce.

The single-use unlock token for attended software updates expires after 20 minutes. In

iOS13 and iPadOS 13.1 or later, the token is stored in a locker protected by the Secure

Enclave. Prior to iOS 13, this token was exported from the Secure Enclave and written

to Effaceable Storage or was protected by the Secure Enclave anti-replay mechanism.

Apolicy timer incremented the counter if the device hadn’t rebooted within 20 minutes.

Unattended software updates occur when the system detects an update is available and

when one of the following is true:

• Automatic updates are configured in iOS12 or later.

• The user chooses Install Later when notified of the update.

After the user enters their passcode, a single-use unlock token is generated and can

remain valid in the Secure Enclave for up to 8 hours. If the update hasn’t yet occurred, this

single-use unlock token is destroyed on every lock and re-created on every subsequent

unlock. Each unlock restarts the 8-hour window. After 8 hours, a policy timer invalidates

the single-use unlock token.

iCloud Backup keybag

The iCloud Backup keybag is similar to the backup keybag. All the class keys in this keybag

are asymmetric (using Curve25519, like the Protected Unless Open Data Protection class).

An asymmetric keybag is also used for the backup in the keychain recovery aspect of

iCloud Keychain.

82Apple Platform Security

Protecting keys in alternative boot modes

Data Protection is designed to provide access to user data only after successful

authentication and only to the authorised user. Data protection classes are designed to

support a variety of use cases, such as the ability to read and write some data even when

a device is locked (but after first unlock). Additional steps are taken to protect access to

user data during alternative boot modes such as those used for Device Firmware Update

(DFU) mode, Recovery mode, Apple Diagnostics or even during software update. These

capabilities are based on a combination of hardware and software features and have been

expanded as Apple-designed silicon has evolved.

Feature A10 A11, S3 A12, S4 A13, S5 A14, A15, S6, S7,

M1 Family

Recovery: All

Data Protection

Classes

protected

Alternative

boots of DFU

mode, Recovery

and software

updates: Class

A, B and C data

protected



The Secure Enclave AES Engine is equipped with lockable software seed bits. When keys

are created from the UID, these seed bits are included in the key derivation function to

create additional key hierarchies. How the seed bit is used varies according to the system

on chip:

• Starting with the Apple A10 and S3 SoCs, a seed bit is dedicated to distinguish keys

protected by the user’s passcode. The seed bit is set for keys that require the user’s

passcode (including Data Protection Class A, Class B and Class C keys) and cleared for

keys that don’t require the user’s passcode (including the file-system metadata key and

Class D keys).

• In iOS13 or later and iPadOS 13.1 or later on devices with an A10 or later, all user data

is rendered cryptographically inaccessible when devices are booted into Diagnostics

mode. This is achieved by introducing an additional seed bit whose setting governs

the ability to access the media key, which itself is needed to access the metadata (and

therefore the contents of all files) on the data volume encrypted with Data Protection.

This protection encompasses files protected in all classes (A, B, C and D), not just

those that required the user’s passcode.

• On A12 SoCs, the Secure Enclave Boot ROM locks the passcode seed bit if the

Application Processor has entered Device Firmware Upgrade (DFU) mode or Recovery

mode. When the passcode seed bit is locked, no operation to change it is allowed. This

is designed to prevent access to data protected with the user’s passcode.

Restoring a device after it enters DFU mode returns it to a known good state with the

certainty that only unmodified Apple-signed code is present. DFU mode can be entered

manually.

83Apple Platform Security

See the following Apple Support articles on how to place a device in DFU mode:

Device Article

i Phone, i Pad, iPodtouch If you forgot your i Phone passcode

AppleTV If you see a warning symbol on AppleTV

A Mac with Apple silicon Revive or restore a Mac with Apple silicon with Apple

Configurator 2

Protecting user data in the face of attack

Attackers attempting to extract user data often try a number of techniques: extracting

the encrypted data to another medium for brute-force attack, manipulating the operating

system version, or otherwise changing or weakening the security policy of the device to

facilitate attack. Attacking data on a device often requires communicating with the device

using physical interfaces like Lightning or USB. Apple devices include features to help

prevent such attacks.

Apple devices support a technology called Sealed Key Protection (SKP) that’s designed

to ensure that cryptographic material is rendered unavailable off device, or that’s used

if manipulations are made to operating system versions or security settings without

appropriate user authorisation. This feature is not provided by the Secure Enclave; instead,

it’s supported by hardware registers that exist at a lower layer in order to provide an

additional layer of protection to the keys necessary to decrypt user data independent of

the Secure Enclave.

Note: SKP is available only on devices with an Apple-designed SoC.

Feature A10 A11, S3 A12, S4 A13, S5 A14, A15, S6, S7,

M1 Family

Sealed Key

Protection

iPhone and iPad can also be configured to only activate data connections in conditions

more likely to indicate the device is still under the physical control of the authorised owner.

Sealed Key Protection (SKP)

On Apple devices that support Data Protection, the key encryption key (KEK) is protected

(or sealed) with measurements of the software on the system, as well as being tied to the

UID available only from the Secure Enclave. On a Mac with Apple silicon, the protection of

the KEK is further strengthened by incorporating information about security policy on the

system because macOS supports critical security policy changes (for example, disabling

secure boot or SIP) that are unsupported on other platforms. On a Mac with Apple silicon,

this protection encompass FileVault keys because FileVault is implemented using Data

Protection (Class C).

84Apple Platform Security

The key that results from entangling the user password, long-term SKP key and Hardware

key 1 (the UID from Secure Enclave) is called the password-derived key. This key is used

to protect the user keybag (on all supported platforms) and KEK (in macOS only), and then

enable biometric unlock or auto unlock with other devices such as AppleWatch.

The Secure Enclave Boot Monitor captures the measurement of the Secure Enclave OS

that is loaded. When the Application Processor Boot ROM measures the Image4 manifest

attached to LLB, that manifest contains a measurement of all other system-paired firmware

that is loaded as well. The LocalPolicy contains the core security configurations for the

macOS that are loaded. The LocalPolicy also contains the nsih field, which is a hash of the

macOS Image4 manifest. The macOS Image4 manifest contains measurements of all the

macOS-paired firmware and core macOS boot objects such as the Boot Kernel Collection

or signed system volume (SSV) root hash.

If an attacker is able to unexpectedly change any of the above measured firmware,

software or security configuration components, it modifies the measurements stored in the

hardware registers. The modification of the measurements causes the crypto-hardware-

derived system measurement root key (SMRK) to derive to a different value, effectively

breaking the seal on the key hierarchy. That causes the system measurement device

key (SMDK) to be inaccessible, which in turn causes the KEK, and thus the data, to be

inaccessible.

However, when the system isn’t under attack, it must accommodate legitimate software

updates that change the firmware measurements and the nsih field in the LocalPolicy to

point at new macOS measurements. In other systems that attempt to incorporate firmware

measurements but that don’t have a known good source of truth, the user is required

to disable the security, update firmware and then re-enable so that a new measurement

baseline can be captured. This significantly increases the risk that the attacker could

tamper with firmware during a software update. The system is helped by the fact that

the Image4 manifest contains all the measurements needed. The hardware that decrypts

the SMDK with the SMRK when the measurements match during a normal boot can also

encrypt the SMDK to a proposed future SMRK. By specifying the measurements that are

expected after a software update, the hardware can encrypt an SMDK, which is accessible

in a current operating system, so that it remains accessible in a future operating system.

Similarly, when a customer legitimately changes their security settings in the LocalPolicy,

the SMDK must be encrypted to the future SMRK based on the measurement for the

LocalPolicy, which LLB computes on the next restart.

85Apple Platform Security

Activating data connections securely in iOS and iPadOS

On iOS or iPadOS devices, if no data connection has been established recently, users must

use FaceID, TouchID or a passcode to activate data connections through a Lightning, USB

or Smart Connector interface. This limits the attack surface against physically connected

devices such as malicious chargers while still enabling usage of other accessories within

reasonable time constraints. If more than an hour has passed since the iOS or iPadOS

device has locked or since an accessory’s data connection has been terminated, the device

won’t allow any new data connections to be established until the device is unlocked.

During this hour period only data connections from accessories that have been previously

connected to the device while in an unlocked state will be allowed. These accessories are

remembered for 30 days after the last time they were connected. Attempts by an unknown

accessory to open a data connection during this period will disable all accessory data

connections over Lightning, USB and Smart Connector until the device is unlocked again.

This hour period:

• Helps ensure that frequent users of connections to a Mac or PC, to accessories or wired

to CarPlay won’t need to enter their passcodes every time they attach their device

• Is necessary because the accessory ecosystem doesn’t provide a cryptographically

reliable way to identify accessories before establishing a data connection

In addition, if it’s been more than 3 days since a data connection has been established with

an accessory, the device will disallow new data connections immediately after it locks. This

is to increase protection for users who don’t often make use of such accessories. Data

connections over Lightning, USB and Smart Connector are also disabled whenever the

device is in a state where it requires a passcode to re-enable biometric authentication.

The user can choose to re-enable always-on data connections in Settings (setting up some

assistive devices does this automatically).

Role of Apple File System

Apple File System (APFS) is a proprietary file system that was designed with encryption

in mind. APFS works across all Apple’s platforms — for iPhone, iPad, iPodtouch, Mac,

AppleTV and AppleWatch. Optimised for Flash/SSD storage, it features strong encryption,

copy-on-write metadata, space sharing, cloning for files and directories, snapshots, fast

directory sizing, atomic safe-save primitives and improved file system fundamentals,

as well as a unique copy-on-write design that uses I/O coalescing to deliver maximum

performance while ensuring data reliability.

Space sharing

APFS allocates storage space on demand. When a single APFS container has multiple

volumes, the container’s free space is shared and can be allocated to any of the individual

volumes as needed. Each volume uses only part of the overall container, so the available

space is the total size of the container minus the space used in all volumes in the

container.

86Apple Platform Security

Multiple volumes

In macOS 10.15 or later, an APFS container used to start up the Mac must contain at least

five volumes, the first three of which are hidden from the user:

• Preboot volume: This volume is unencrypted and contains data needed for booting each

system volume in the container.

• VM volume: This volume is unencrypted and is used by macOS for storing encrypted

swap files.

• Recovery volume: This volume is unencrypted and must be available without unlocking a

system volume in order to start up in recoveryOS.

• System volume: Contains the following:

• All the necessary files to start up the Mac

• All apps installed natively by macOS (apps that used to reside in the /Applications

folder now reside in /System/Applications)

Note: By default, no processes can write to the System volume, including Apple system

processes.

• Data volume: Contains data that is subject to change, such as:

• Any data inside the user’s folder, including photos, music, videos and documents

• Apps the user installed, including AppleScript and Automator applications

• Custom frameworks and daemons installed by the user, organisation or third-party apps

• Other locations owned and writable by the user, such as /Applications, /Library,

/Users, /Volumes, /usr/local, /private, /var and /tmp

A data volume is created for each additional system volume. The preboot, VM and recovery

volumes are all shared and not duplicated.

In macOS11 or later, the system volume is captured in a snapshot. The operating system

boots from a snapshot of the system volume, not just from a read-only mount of the

mutable system volume.

In iOS and iPadOS, storage is divided into at least two APFS volumes:

• System volume

• Data volume

Keychain data protection

Many apps need to handle passwords and other short but sensitive bits of data, such

as keys and login tokens. The keychain provides a secure way to store these items. The

various Apple operating systems use differing mechanisms to enforce the guarantees

associated with the different keychain protection classes. In macOS (including a Mac with

Apple silicon), Data Protection is not used directly to enforce these guarantees.

87Apple Platform Security

Overview

Keychain items are encrypted using two different AES-256-GCM keys: a table key

(metadata) and a per-row key (secret key). Keychain metadata (all attributes other than

kSecValue) is encrypted with the metadata key to speed searches and the secret value

(kSecValueData) is encrypted with the secret key. The metadata key is protected by the

Secure Enclave but is cached in the Application Processor to allow fast queries of the

keychain. The secret key always requires a round trip through the Secure Enclave.

The keychain is implemented as a SQLite database, stored on the file system. There is only

one database and the securityd daemon determines which keychain items each process

or app can access. Keychain Access APIs result in calls to the daemon, which queries

the app’s “Keychain-access-groups”, “application-identifier” and “application-group”

entitlements. Rather than limiting access to a single process, access groups allow keychain

items to be shared between apps.

Keychain items can be shared only between apps from the same developer. To share

keychain items, third-party apps use access groups with a prefix allocated to them through

the Apple Developer Programme in their application groups. The prefix requirement and

application group uniqueness are enforced through code signing, provisioning profiles and

the Apple Developer Programme.

Keychain data is protected using a class structure similar to the one used in file Data

Protection. These classes have behaviours equivalent to file Data Protection classes but

use distinct keys and functions.

Availability File data protection Keychain data protection

When unlocked NSFile Protection Complete k Sec Attr Accessible When

Unlocked

While locked NSFile Protection Complete Unless Open N/A

After first unlock NSFile Protection Complete Until First User Authentication k Sec Attr Accessible After

First Unlock

Always NSFile Protection None k Sec Attr Accessible Always

Passcode enabled N/A k Sec Attr Accessible When

Passcode Set This Device

Only

Apps that use background refresh services can use kSecAttrAccessibleAfterFirstUnlock for

keychain items that need to be accessed during background updates.

The class kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly behaves the same

as kSecAttrAccessibleWhenUnlocked; however, it’s available only when the device is

configured with a passcode. This class exists only in the system keybag; they:

• Don’t sync to iCloud Keychain

• Aren’t backed up

• Aren’t included in escrow keybags

If the passcode is removed or reset, the items are rendered useless by discarding the

class keys.

88Apple Platform Security

Other keychain classes have a “This device only” counterpart, which is always protected

with the UID when being copied from the device during a backup, rendering it useless

if restored to a different device. Apple has carefully balanced security and usability by

choosing keychain classes that depend on the type of information being secured and when

it’s needed by iOS and iPadOS. For example, a VPN certificate must always be available so

the device keeps a continuous connection, but it’s classified as “non-migratory”, so it can’t

be moved to another device.

Keychain data class protections

The class protections listed below are enforced for keychain items.

Item Accessible

Wi-Fi passwords After first unlock

Mail accounts After first unlock

Microsoft Exchange Active Sync accounts After first unlock

VPN passwords After first unlock

LDAP, Cal DAV, Card DAV After first unlock

Social network account tokens After first unlock

Handoff advertisement encryption keys After first unlock

i Cloud token After first unlock

i Message keys After first unlock

Home sharing password When unlocked

Safari passwords When unlocked

Safari bookmarks When unlocked

Finder/i Tunes backup When unlocked, non-migratory

Private keys installed by a configuration profile When unlocked, non-migratory

VPN certificates Always, non-migratory

Bluetooth® keys Always, non-migratory

Apple Push Notification service (APNs) token Always, non-migratory

i Cloud certificates and private key Always, non-migratory

SIM PIN Always, non-migratory

Certificates installed by a configuration profile Always

Find My token Always

Voicemail Always

89Apple Platform Security

Keychain access control

Keychains can use access control lists (ACLs) to set policies for accessibility and

authentication requirements. Items can establish conditions that require user presence

by specifying that they can’t be accessed unless authenticated using FaceID, TouchID,

or by entering the device’s passcode or password. Access to items can also be limited by

specifying that FaceID or TouchID enrolment hasn’t changed since the item was added.

This limitation helps prevent an attacker from adding their own fingerprint to access a

keychain item. ACLs are evaluated inside the Secure Enclave and are released to the kernel

only if their specified constraints are met.

Keychain architecture in macOS

macOS also provides access to the keychain to conveniently and securely store usernames

and passwords, digital identities, encryption keys and secure notes. It can be accessed by

opening the Keychain Access app in /Applications/Utilities/. Using a keychain eliminates the

requirement to enter — or even remember — the credentials for each resource. An initial

default keychain is created for each Mac user, though users can create other keychains for

specific purposes.

In addition to relying on user keychains, macOS relies on a number of system-level

keychains that maintain authentication assets that aren’t user specific, such as network

credentials and public key infrastructure (PKI) identities. One of these keychains, System

Roots, is immutable and stores internet PKI root certificate authority (CA) certificates to

facilitate common tasks like online banking and e-commerce. The user can similarly deploy

internally provisioned CA certificates to managed Mac computers to help validate internal

sites and services.

FileVault

Volume encryption with FileVault in macOS

Mac computers offer FileVault, a built-in encryption capability, to secure all data at rest.

FileVault uses the AES-XTS data encryption algorithm to protect full volumes on internal

and removable storage devices.

FileVault on a Mac with Apple silicon is implemented using Data Protection Class C with a

volume key. On a Mac with the Apple T2 Security Chip as well as a Mac with Apple silicon,

encrypted internal storage devices directly connected to the Secure Enclave leverage

its hardware security capabilities as well as that of the AES engine. After a user turns on

FileVault on a Mac, their credentials are required during the boot process.

90Apple Platform Security

Internal storage with FileVault turned on

Without valid login credentials or a cryptographic recovery key, the internal APFS volumes

remain encrypted and are protected from unauthorised access even if the physical storage

device is removed and connected to another computer. In macOS 10.15, this includes

both the system volume and the data volume. Starting in macOS 11, the system volume

is protected by the signed system volume (SSV) feature, but the data volume remains

protected by encryption. Internal volume encryption on a Mac with Apple silicon as well as

those with the T2 chip is implemented by constructing and managing a hierarchy of keys,

and builds on the hardware encryption technologies built into the chip. This hierarchy of

keys is designed to simultaneously achieve four goals:

• Require the user’s password for decryption

• Protect the system from a brute-force attack directly against storage media removed

from Mac

• Provide a swift and secure method for wiping content via deletion of necessary

cryptographic material

• Enable users to change their password (and in turn the cryptographic keys used to

protect their files) without requiring re-encryption of the entire volume

On a Mac with Apple silicon and those with the T2 chip, all FileVault key handling occurs

in the Secure Enclave; encryption keys are never directly exposed to the Intel CPU. All

APFS volumes are created with a volume encryption key by default. Volume and metadata

contents are encrypted with this volume encryption key, which is wrapped with the class

key. The class key is protected by a combination of the user’s password and the hardware

UID when FileVault is turned on.

Internal storage with FileVault turned off

If FileVault isn’t turned on in a Mac with Apple silicon or a Mac with the T2 chip during the

initial Setup Assistant process, the volume is still encrypted but the volume encryption key

is protected only by the hardware UID in the Secure Enclave.

91Apple Platform Security

If FileVault is turned on later — a process that is immediate because the data has already

been encrypted — an anti-replay mechanism helps prevent the old key (based on hardware

UID only) from being used to decrypt the volume. The volume is then protected by a

combination of the user password with the hardware UID as previously described.

Deleting FileVault volumes

When deleting a volume, its volume encryption key is securely deleted by the Secure

Enclave. This helps prevent future access with this key even by the Secure Enclave. In

addition, all volume encryption keys are wrapped with a media key. The media key doesn’t

provide additional confidentiality of data; instead, it’s designed to enable swift and secure

deletion of data because without it decryption is impossible.

On a Mac with Apple silicon and those with the T2 chip, the media key is guaranteed to

be erased by the Secure Enclave–supported technology — for example by remote MDM

commands. Erasing the media key in this manner renders the volume cryptographically

inaccessible.

Removable storage devices

Encryption of removable storage devices doesn’t utilise the security capabilities of the

Secure Enclave, and its encryption is performed in the same manner as an Intel-based Mac

without the T2 chip.

Managing FileVault in macOS

In macOS, organisations can manage FileVault using SecureToken or Bootstrap Token.

Using Secure Token

Apple File System (APFS) in macOS 10.13 or later changes how FileVault encryption keys

are generated. In previous versions of macOS on CoreStorage volumes, the keys used

in the FileVault encryption process were created when a user or organisation turned on

FileVault on a Mac. In macOS on APFS volumes, the keys are generated either during user

creation, setting the first user’s password, or during the first login by a user of the Mac.

This implementation of the encryption keys, when they’re generated and how they’re

stored are all part of a feature known as Secure Token. Specifically, a secure token is a

wrapped version of a key-encryption key (KEK) protected by a user’s password.

When deploying FileVault on APFS, the user can continue to:

• Use existing tools and processes, such as a personal recovery key (PRK) that can be

stored with a mobile device management (MDM) solution for escrow

• Create and use an institutional recovery key (IRK)

• Defer enablement of FileVault until a user logs in to or out of the Mac

In macOS 11, setting the initial password for the very first user on the Mac results in

that user being granted a secure token. In some workflows, that may not be the desired

behaviour as previously, granting the first secure token would have required the user

account to log in. To prevent this from happening, add ;DisabledTags;SecureToken to

the programmatically created user’s AuthenticationAuthority attribute prior to setting

the user’s password, as shown below:

sudo dscl . append /Users/<user name> AuthenticationAuthority

";DisabledTags;SecureToken"

92Apple Platform Security

Using Bootstrap Token

macOS 10.15 introduced a new feature — Bootstrap Token — to help with granting a secure

token to both mobile accounts and the optional device enrolment–created administrator

account (“managed administrator”). In macOS 11, a bootstrap token can grant a secure

token to any user logging in to a Mac computer, including local user accounts. Using the

Bootstrap Token feature of macOS 10.15 or later requires:

• Mac enrolment in MDM using Apple School Manager or Apple Business Manager, which

makes the Mac supervised

• MDM vendor support

In macOS 10.15.4 or later, a bootstrap token is generated and escrowed to MDM on the first

A bootstrap token can also be generated and escrowed to MDM using the profiles

command-line tool, if needed.

In macOS 11, a bootstrap token may also be used for more than just granting secure token

to user accounts. On a Mac with Apple silicon, a bootstrap token, if available, can be used

to authorise the installation of both kernel extensions and software updates when managed

using MDM.

How Apple protects users’ personal data

Protecting app access to user data

In addition to encrypting data at rest, Apple devices help prevent apps from accessing a

user’s personal information without permission using various technologies including Data

Vault. In Settings in iOS and iPadOS, or System Preferences in macOS, users can see which

apps they have permitted to access certain information as well as grant or revoke any

future access. Access is enforced in the following:

• iOS, iPadOS and macOS: Calendars, Camera, Contacts, Microphone, Photos, Reminders,

Speech recognition

• iOS and iPadOS: Bluetooth, Home, Media, Media apps and Apple Music, Motion and

fitness

• iOS and watchOS: Health

• macOS: Input monitoring (for example, keyboard strokes), Prompt, Screen recording

(for example, static screen shots and video), System Preferences

In iOS 13.4 or later and iPadOS 13.4 or later, all third-party apps automatically have their

data protected in a Data Vault. Data Vault helps protect against unauthorised access to the

data, even from processes that aren’t themselves sandboxed. Additional classes in iOS15

or later include Local Network, Nearby Interactions, Research Sensor & Usage Data, and

Focus.

If the user signs in to iCloud, apps in iOS and iPadOS are granted access to iCloud Drive

by default. Users may control each app’s access under iCloud in Settings. iOS and iPadOS

also provide restrictions designed to prevent data movement between apps and accounts

installed by a mobile device management (MDM) solution and those installed by the user.

93Apple Platform Security

Protecting access to user’s health data

HealthKit provides a central repository for health and fitness data on iPhone and

AppleWatch. HealthKit also works directly with health and fitness devices, such as

compatible Bluetooth Low Energy (BLE) heart rate monitors and the motion coprocessor

built into many iOS devices. All HealthKit interaction with health and fitness apps,

healthcare institutions, and health and fitness devices require the permission of the user.

This data is stored in the Data Protection class Protected Unless Open. Access to the data

is relinquished 10 minutes after the device locks, and data becomes accessible the next

time the user enters their passcode or uses FaceID or TouchID to unlock the device.

Collecting and storing health and fitness data

HealthKit also collects and stores management data, such as access permissions for apps,

names of devices connected to HealthKit and scheduling information used to launch apps

when new data is available. This data is stored in the Data Protection class Protected Until

First User Authentication. Temporary journal files store health records that are generated

when the device is locked, such as when the user is exercising. These are stored in the

Data Protection class Protected Unless Open. When the device is unlocked, the temporary

journal files are imported into the primary health databases then deleted when the merge is

completed.

Health data can be stored in iCloud. End-to-end encryption for Health data requires

iOS12 or later and two-factor authentication. Otherwise, the user’s data is still encrypted

in storage and transmission but isn’t encrypted end-to-end. After the user turns on

two-factor authentication and updates to iOS12 or later, the user’s health data is migrated

to end-to-end encryption.

If the user backs up their device using the Finder (macOS 10.15 or later) or iTunes

(macOS 10.14 or earlier), health data is stored only if the backup is encrypted.

Clinical health records

Users can sign in to supported health systems within the Health app to obtain a copy

of their clinical health records. When connecting a user to a health system, the user

authenticates using OAuth 2 client credentials. After connecting, clinical health record data

is downloaded directly from the health institution using a TLS 1.3 protected connection.

Once downloaded, clinical health records are securely stored alongside other health data.

Health data integrity

Data stored in the database includes metadata to track the provenance of each data

record. This metadata includes an app identifier that identifies which AppStored the

record. Additionally, an optional metadata item can contain a digitally signed copy of the

record. This is intended to provide data integrity for records generated by a trusted device.

The format used for the digital signature is the Cryptographic Message Syntax (CMS)

specified in RFC 5652.

94Apple Platform Security

Health data access by third-party apps

Access to the HealthKit API is controlled with entitlements and apps must conform to

restrictions about how the data is used. For example, apps aren’t allowed to use health

data for advertising. Apps are also required to provide users with a privacy policy that

details its use of health data.

Access to health data by apps is controlled by the user’s Privacy settings. Users are asked

to grant access when apps request access to health data, similar to Contacts, Photos and

other iOS data sources. However, with health data, apps are granted separate access for

reading and writing data as well as separate access for each type of health data. Users can

view, and revoke, permissions they’ve granted for accessing health data under Settings >

Health > Data Access & Devices.

If granted permission to write data, apps can also read the data they write. If granted

permission to read data, apps can read data written by all sources. However, apps can’t

determine access granted to other apps. In addition, apps can’t conclusively tell whether

they’ve been granted read access to health data. When an app doesn’t have read access,

all queries return no data — the same response that an empty database would return. This

is designed to prevent apps from inferring the user’s health status by learning which types

of data the user is tracking.

Medical ID for users

The Health app gives users the option of filling in a Medical ID form with information that

could be important during a medical emergency. The information is entered or updated

manually and isn’t synced with the information in the health databases.

The Medical ID information is viewed by tapping the Emergency button on the Lock Screen.

The information is stored on the device using the Data Protection class No Protection so

that it’s accessible without having to enter the device passcode. Medical ID is an optional

feature that lets users decide how to balance both safety and privacy concerns. This

data is backed up in iCloud Backup in iOS13 or earlier. In iOS 14, Medical ID is synced

between devices using CloudKit and has the same encryption characteristics as the rest of

health data.

Health sharing

In iOS 15, the Health app gives users the option of sharing their Health data with other

users. Health data is shared between the two users using end-to-end iCloud encryption,

and Apple can’t access data that is sent through Health sharing. To use the feature,

both the sending and receiving users must be using iOS15 or later and have two-factor

authentication enabled.

Users can also choose to share their Health data with their healthcare provider using

the Share with Provider feature in the Health app. Data shared using this feature is made

available only to the health institutions selected by the user using end-to-end encryption,

and Apple doesn’t maintain or have access to the encryption keys to decrypt, view or

otherwise access the Health data shared through the Share with Provider feature. Further

details about how the design of this service protects users’ Health data can be found in the

Security and Privacy section of the Apple Registration Guide for Healthcare Organizations.

95Apple Platform Security

Digital signing and encryption

Access control lists

Keychain data is partitioned and protected with access control lists (ACLs). As a result,

credentials stored by third-party apps can’t be accessed by apps with different identities

unless the user explicitly approves them. This protection provides a mechanism for

securing authentication credentials in Apple devices across a range of apps and services

within the organisation.

Mail

In the Mail app, users can send messages that are digitally signed and encrypted. Mail

automatically discovers appropriate RFC 5322 case-sensitive email address subject

or subject alternative names on digital signing and encryption certificates on attached

Personal Identification Verification (PIV) tokens in compatible smart cards. If a configured

email account matches an email address on a digital signing or encryption certificate on an

attached PIV token, Mail automatically displays the signing button in the toolbar of a new

message window. If Mail has the recipient’s email encryption certificate or can discover it

in the Microsoft Exchange global address list (GAL), an unlocked icon appears in the new

message toolbar. A locked lock icon indicates the message will be sent encrypted with the

recipient’s public key.

Per-message S/MIME

iOS, iPadOS and macOS support per-message S/MIME. This means that S/MIME users can

choose to always sign and encrypt messages by default or to selectively sign and encrypt

individual messages.

Identities used with S/MIME can be delivered to Apple devices using a configuration profile,

a mobile device management (MDM) solution, the Simple Certificate Enrolment Protocol

(SCEP) or Microsoft Active Directory Certificate Authority.

96Apple Platform Security

Smart cards

macOS 10.12 or later includes native support for PIV cards. These cards are widely used in

commercial and government organisations for two-factor authentication, digital signing and

encryption.

Smart cards include one or more digital identities that have a pair of public and private

keys and an associated certificate. Unlocking a smart card with the personal identification

number (PIN) provides access to the private keys used for authentication, encryption and

signing operations. The certificate determines what a key can be used for, what attributes

are associated with it and whether it’s validated (signed) by a certificate authority (CA)

certificate.

Smart cards can be used for two-factor authentication. The two factors needed to unlock

a card are “something the user has” (the card) and “something the user knows” (the PIN).

macOS 10.12 or later also has native support for smart card Login Window authentication

and client certificate authentication to websites on Safari. It also supports Kerberos

authentication using key pairs (PKINIT) for single sign-on to Kerberos-supported services.

To learn more about smart cards and macOS, see Intro to smart card integration in

ApplePlatform Deployment.

Encrypted disk images

In macOS, encrypted disk images serve as secure containers in which users can store or

transfer sensitive documents and other files. Encrypted disk images are created using Disk

Utility, located in /Applications/Utilities/. Disk images can be encrypted using either 128-bit

or 256-bit AES encryption. Because a mounted disk image is treated as a local volume

connected to a Mac, users can copy, move and open files and folders stored in it. As with

FileVault, the contents of a disk image are encrypted and decrypted in real time. With

encrypted disk images, users can safely exchange documents, files and folders by saving

an encrypted disk image to removable media, sending it as a mail message attachment

or storing it on a remote server. For more information on encrypted disk images, see the

DiskUtility User Guide.

97Apple Platform Security

App security

App security overview

Today, apps are among the most critical elements of a security architecture. Even as apps

provide amazing productivity benefits for users, they also have the potential to negatively

impact system security, stability and user data if they’re not handled properly.

Because of this, Apple provides layers of protection to help ensure that apps are free

of known malware and haven’t been tampered with. Additional protections enforce that

access from apps to user data is carefully mediated. These security controls provide a

stable, secure platform for apps, enabling thousands of developers to deliver hundreds of

thousands of apps for iOS, iPadOS and macOS — all without impacting system integrity.

And users can access these apps on their Apple devices without undue fear of viruses,

malware or unauthorised attacks.

On iPhone, iPad and iPodtouch, all apps are obtained from the AppStore — and all apps

are sandboxed — to provide the tightest controls.

On Mac, many apps are obtained from the AppStore, but Mac users also download and use

apps from the internet. To safely support internet downloading, macOS layers additional

controls. First, by default in macOS 10.15 or later, all Mac apps need to be notarised by

Apple to launch. This requirement helps to ensure these apps are free of known malware,

without requiring that the apps be provided through the AppStore. In addition, macOS

includes state-of-the-art antivirus protection to block — and if necessary remove —

malware.

98Apple Platform Security

As an additional control across platforms, sandboxing helps protect user data from

unauthorised access by apps. And in macOS, data in critical areas is itself protected —

which helps ensure that users remain in control of access to files in Desktop, Documents,

Downloads and other areas from all apps, whether the apps attempting access are

themselves sandboxed or not.

Native capability Third-party equivalent

Plug-in unapproved list, Safari extension unapproved list Virus/Malware definitions

File Quarantine Virus/Malware definitions

XProtect/YARA signatures Virus/Malware definitions; endpoint protection

Gatekeeper Endpoint protection; enforces code signing on apps

to help ensure that only trusted software runs

eficheck

(Necessary for a Mac without an Apple T2 Security Chip)

Endpoint protection; rootkit detection

Application firewall Endpoint protection; firewalling

Packet Filter (pf) Firewall solutions

System Integrity Protection Built into macOS

Mandatory Access Controls Built into macOS

Kext exclude list Built into macOS

Mandatory app code signing Built into macOS

App notarisation Built into macOS

App security in iOS and iPadOS

Intro to app security for iOS and iPadOS

Unlike other mobile platforms, iOS and iPadOS don’t allow users to install potentially

malicious unsigned apps from websites or to run untrusted apps. At runtime, code

signature checks that all executable memory pages are made as they are loaded to help

ensure that an app hasn’t been modified since it was installed or last updated.

After an app is verified to be from an approved source, iOS and iPadOS enforce security

measures designed to prevent it from compromising other apps or the rest of the system.

99Apple Platform Security

App code signing process in iOS and iPadOS

In iOS and iPadOS, Apple offers app security through such things as mandatory code

signing, strict developer sign-in and more.

Mandatory code signing

After the iOS or iPadOS kernel has started, it controls which user processes and apps

can be run. To help ensure that all apps come from a known and approved source and

haven’t been tampered with, iOS and iPadOS require that all executable code be signed

using an Apple-issued certificate. Apps provided with the device, like Mail and Safari,

are signed by Apple. Third-party apps must also be validated and signed using an Apple-

issued certificate. Mandatory code signing extends the concept of chain of trust from the

operating system to apps and helps prevent third-party apps from loading unsigned code

resources or using self-modifying code.

How developers sign their apps

Developers can sign their apps through certificate validation (through the Apple Developer

Programme). They can also embed frameworks inside their apps and have that code

validated with an Apple-issued certificate (through a team identifier string).

• Certificate validation: To develop and install apps in iOS or iPadOS devices, developers

must register with Apple and join the Apple Developer Programme. The real-world

identity of each developer, whether an individual or a business, is verified by Apple

before their certificate is issued. This certificate allows developers to sign apps and

submit them to the AppStore for distribution. As a result, all apps in the AppStore

have been submitted by an identifiable person or organisation, serving as a deterrent to

the creation of malicious apps. They have also been reviewed by Apple to help ensure

they generally operate as described and don’t contain obvious bugs or other notable

problems. In addition to the technology already discussed, this curation process gives

users confidence in the quality of the apps they buy.

• Code signature validation: iOS and iPadOS allow developers to embed frameworks

inside of their apps, which can be used by the app itself or by extensions embedded

within the app. To protect the system and other apps from loading third-party code

inside their address space, the system performs a code signature validation of all

the dynamic libraries that a process links against at launch time. This verification

is accomplished through the team identifier (Team ID), which is extracted from an

Apple-issued certificate. A team identifier is a 10-character alphanumeric string — for

example, 1A2B3C4D5F. A program may link against any platform library that ships with

the system or any library with the same team identifier in its code signature as the main

executable. Since the executables shipping as part of the system don’t have a team

identifier, they can only link against libraries that ship with the system itself.

100Apple Platform Security

Verifying proprietary in-house apps

Eligible businesses also have the ability to write proprietary in-house apps for use within

their organisation and to distribute them to their employees. Businesses and organisations

can apply to the Apple Developer Enterprise Programme (ADEP). For more information and

to review eligibility requirements, see the Apple Developer Enterprise Programme website.

After an organisation becomes a member of ADEP, it can register to obtain a provisioning

profile that permits proprietary in-house apps to run on devices it authorises.

Users must have the provisioning profile installed to run these apps. This helps ensure that

only the organisation’s intended users are able to load the apps onto their iOS and iPadOS

devices. Apps installed through mobile device management (MDM) are implicitly trusted

because the relationship between the organisation and the device is already established.

Otherwise, users have to approve the app’s provisioning profile in Settings. Organisations

can also restrict users from approving apps from unknown developers. On first launch of

any proprietary in-house app, the device must receive positive confirmation from Apple

that the app is allowed to run.

Security of runtime process in iOS and iPadOS

iOS and iPadOS help ensure runtime security by using a “sandbox”, declared entitlements

and Address Space Layout Randomisation (ASLR).

Sandboxing

All third-party apps are “sandboxed”, so they are restricted from accessing files stored by

other apps or from making changes to the device. Sandboxing is designed to prevent apps

from gathering or modifying information stored by other apps. Each app has a unique home

directory for its files, which is randomly assigned when the app is installed. If a third-party

app needs to access information other than its own, it does so only by using services

explicitly provided by iOS and iPadOS.

System files and resources are also shielded from the users’ apps. Most iOS and iPadOS

system files and resources run as the non-privileged user “mobile”, as do all third-party

apps. The entire operating system partition is mounted as read-only. Unnecessary tools,

such as remote login services, aren’t included in the system software, and APIs don’t allow

apps to escalate their own privileges to modify other apps or iOS and iPadOS.

Use of entitlements

Access by third-party apps to user information, and to features such as iCloud and

extensibility, is controlled using declared entitlements. Entitlements are key value pairs that

are signed in to an app and allow authentication beyond runtime factors, like UNIX user

ID. Since entitlements are digitally signed, they can’t be changed. Entitlements are used

extensively by system apps and daemons to perform specific privileged operations that

would otherwise require the process to run as root. This greatly reduces the potential for

privilege escalation by a compromised system app or daemon.

In addition, apps can only perform background processing through system-provided APIs.

This allows apps to continue to function without degrading performance or dramatically

impacting battery life.

101Apple Platform Security

Address Space Layout Randomisation

Address Space Layout Randomisation (ASLR) helps protect against the exploitation of

memory corruption bugs. Built-in apps use ASLR to help randomise all memory regions

upon launch. In addition to work upon launch, ASLR randomly arranges the memory

addresses of executable code, system libraries and related programming constructs,

further reducing the likelihood of many exploits. For example, a return-to-libc attack

attempts to trick a device into executing malicious code by manipulating memory

addresses of the stack and system libraries. Randomising the placement of these makes

the attack more difficult to execute, especially across multiple devices. Xcode and the iOS

or iPadOS development environments automatically compile third-party programs with

ASLR support turned on.

Execute Never feature

Further protection is provided by iOS and iPadOS using ARM’s Execute Never (XN) feature,

which marks memory pages as non-executable. Memory pages marked as both writable

and executable can be used only by apps under tightly controlled conditions: The kernel

checks for the presence of the Apple-only dynamic code-signing entitlement. Even then,

only a single mmap call can be made to request an executable and writable page, which is

given a randomised address. Safari uses this functionality for its JavaScript Just-in-Time

(JIT) compiler.

Supporting extensions in iOS, iPadOS and macOS

iOS, iPadOS and macOS allow apps to provide functionality to other apps by providing

extensions. Extensions are special-purpose signed executable binaries packaged within

an app. During installation, the system automatically detects extensions and makes them

available to other apps using a matching system.

Extension points

A system area that supports extensions is called an extension point. Each extension point

provides APIs and enforces policies for that area. The system determines which extensions

are available based on extension point–specific matching rules. The system automatically

launches extension processes as needed and manages their lifetime. Entitlements can be

used to restrict extension availability to particular system apps. For example, a Today view

widget appears only in Notification Centre and a sharing extension is available only from

the Sharing pane. Examples of extension points are Today widgets, Share, Actions, Photo

Editing, File Provider and Custom Keyboard.

How extensions communicate

Extensions run in their own address space. Communication between the extension and the

app from which it was activated uses interprocess communications mediated by the system

framework. They don’t have access to each other’s files or memory spaces. Extensions are

designed to be isolated from each other, from their containing apps and from the apps that

use them. They are sandboxed like any other third-party app and have a container separate

from the containing app’s container. However, they share the same access to privacy

controls as the container app. So if a user grants Contacts access to an app, this grant is

extended to the extensions that are embedded within the app but not to the extensions

activated by the app.

102Apple Platform Security

How custom keyboards are used

Custom keyboards are a special type of extension because it’s enabled by the user for the

entire system. After it’s enabled, a keyboard extension is used for any text field except

the passcode input and any secure text view. To restrict the transfer of user data, custom

keyboards, by default, run in a very restrictive sandbox that blocks access to the network,

to services that perform network operations on behalf of a process and to APIs that would

allow the extension to exfiltrate typing data. Developers of custom keyboards can request

that their extension have Open Access, which lets the system run the extension in the

default sandbox after getting consent from the user.

MDM and extensions

For devices enrolled in a mobile device management (MDM) solution, document and keyboard

extensions obey Managed Open In rules. For example, the MDM solution can help prevent

users from exporting a document from a managed app to an unmanaged Document Provider,

or help prevent them from using an unmanaged keyboard with a managed app. Additionally,

app developers can prevent the use of third-party keyboard extensions within their app.

App protection and app groups in iOS and iPadOS

In iOS and iPadOS, organisations can protect apps securely by using the iOS SDK and by

joining an App Group at the Apple Developer Portal.

Adopting Data Protection in apps

The iOS Software Development Kit (SDK) for iOS and iPadOS offers a full suite of APIs that

make it easy for third-party and in-house developers to adopt Data Protection and help

ensure the highest level of protection in their apps. Data Protection is available for file and

database APIs, including NSFileManager, CoreData, NSData and SQLite.

The Mail app database (including attachments), managed books, Safari bookmarks, app

launch images and location data are also stored through encryption, with keys protected

by the user’s passcode on their device. Calendar (excluding attachments), Contacts,

Reminders, Notes, Messages and Photos implement the Data Protection entitlement

Protected Until First User Authentication.

User-installed apps that don’t opt in to a specific Data Protection class receive Protected

Until First User Authentication by default.

Joining an App Group

Apps and extensions owned by a given developer account can share content when

configured to be part of an App Group. It’s up to the developer to create the appropriate

groups on the Apple Developer Portal and include the desired set of apps and extensions.

Once configured to be part of an App Group, apps have access to the following:

• A shared on-volume container for storage which stays on the device as long as at least

one app from the group is installed

• Shared preferences

• Shared keychain items

The Apple Developer Portal helps ensure that App group IDs (GIDs) are unique across the

app ecosystem.

103Apple Platform Security

Verifying accessories in iOS and iPadOS

The Made for iPhone, iPad and iPodtouch (MFi) licensing programme provides vetted

accessory manufacturers access to the iPod Accessories Protocol (iAP) and the necessary

supporting hardware components.

When an MFi accessory communicates with an iOS or iPadOS device using a Lightning or

USB-C connector or through Bluetooth, the device asks the accessory to prove it’s been

authorised by Apple by responding with an Apple-provided certificate, which is verified by

the device. The device then sends a challenge which the accessory must answer with a

signed response. This process is entirely handled by a custom integrated circuit (IC) that

Apple provides to approved accessory manufacturers and is transparent to the accessory

itself.

Accessories can request access to different transport methods and functionality — for

example, access to digital audio streams over the Lightning or USB-C cable, or location

information provided over Bluetooth. An authentication IC is designed to ensure that

only approved accessories are granted full access to the device. If an accessory doesn’t

support authentication, its access is limited to analogue audio and a small subset of serial

(UART) audio playback controls.

AirPlay also uses the authentication IC to verify that receivers have been approved by

Apple. AirPlay audio and CarPlay video streams use the MFi-SAP (Secure Association

Protocol), which encrypts communication between the accessory and device using

AES128 in counter (CTR) mode. Ephemeral keys are exchanged using ECDH key exchange

(Curve25519) and signed using the authentication IC’s 1024-bit RSA key as part of the

Station-to-Station (STS) protocol.

App security in macOS

Intro to app security for macOS

App security in macOS consists of a number of overlapping layers — the first of which is

the option to run only signed and trusted apps from the AppStore. In addition, macOS

layers protections to help ensure that apps downloaded from the internet are free of

known malware. macOS offers technologies to detect and remove malware, and offers

additional protections designed to prevent untrusted apps from accessing user data.

Apple services such as Notarisation and XProtect updates are designed to help prevent

malware installation. When necessary, these services locate malware that may have at first

avoided detection and then quickly and efficiently remove it. Ultimately, macOS users are

free to operate within the security model that makes sense for them — including running

completely unsigned and untrusted code.

104Apple Platform Security

App code signing process in macOS

All apps from the AppStore are signed by Apple. This signing is designed to ensure that they

haven’t been tampered with or altered. Apple signs any apps provided with Apple devices.

In macOS 10.15, all apps distributed outside the AppStore must be signed by the developer

using an Apple-issued Developer ID certificate (combined with a private key) and notarised

by Apple to run under the default Gatekeeper settings. Apps developed in-house should

also be signed with an Apple-issued Developer ID so that users can validate their integrity.

In macOS, code signing and notarisation work independently — and can be performed by

different actors — for different goals. Code signing is performed by the developer using

their Developer ID certificate (issued by Apple) and verification of this signature proves

to the user that a developer’s software hasn’t been tampered with since the developer

built and signed it. Notarisation can be performed by anyone in the software distribution

chain and proves that Apple has been provided a copy of the code to check for malware

and no known malware was found. The output of Notarisation is a ticket which is stored on

Apple servers and can be optionally stapled to the app (by anyone) without invalidating the

signature of the developer.

Mandatory Access Controls (MACs) require code signing to enable entitlements protected

by the system. For example, apps requiring access through the firewall must be code

signed with the appropriate MAC entitlement.

Gatekeeper and runtime protection in macOS

macOS offers the Gatekeeper technology and runtime protection to help ensure that only

trusted software runs on a user’s Mac.

Gatekeeper

macOS includes a security technology called Gatekeeper, which is designed to help ensure

that only trusted software runs on a user’s Mac. When a user downloads and opens an

app, a plug-in or an installer package from outside the AppStore, Gatekeeper verifies that

the software is from an identified developer, is notarised by Apple to be free of known

malicious content and hasn’t been altered. Gatekeeper also requests user approval before

opening downloaded software for the first time to make sure the user hasn’t been tricked

into running executable code they believed to simply be a data file.

By default, Gatekeeper helps ensure that all downloaded software has been signed by the

AppStore or signed by a registered developer and notarised by Apple. Both the AppStore

review process and the notarisation pipeline are designed to ensure that apps contain

no known malware. Therefore, by default all software in macOS is checked for known

malicious content the first time it’s opened, regardless of how it arrived on the Mac.

Users and organisations have the option to allow only software installed from the

AppStore. Alternatively, users can override Gatekeeper policies to open any software

unless restricted by a mobile device management (MDM) solution. Organisations can use

MDM to configure Gatekeeper settings, including allowing software signed with alternative

identities. Gatekeeper can also be completely disabled, if necessary.

Gatekeeper also protects against the distribution of malicious plug-ins with benign apps.

Here, using the app triggers the loading of a malicious plug-in without the user’s knowledge.

When necessary, Gatekeeper opens apps from randomised, read-only locations. This is

designed to prevent the automatic loading of plug-ins distributed alongside the app.

105Apple Platform Security

Runtime protection

System files, resources and the kernel are shielded from a user’s app space. All apps from

the AppStore are sandboxed to restrict access to data stored by other apps. If an app from

the AppStore needs to access data from another app, it can do so only by using the APIs

and services provided by macOS.

Protecting against malware in macOS

Apple operates a threat intelligence process to quickly identify and block malware.

Three layers of defence

Malware defences are structured in three layers:

1. Prevent launch or execution of malware: AppStore, or Gatekeeper combined with

Notarisation

2. Block malware from running on customer systems: Gatekeeper, Notarisation and XProtect

3. Remediate malware that has executed: XProtect

The first layer of defence is designed to inhibit the distribution of malware, and prevent it

from launching even once — this is the goal of the AppStore, and Gatekeeper combined

with Notarisation.

The next layer of defence is to help ensure that if malware appears on any Mac, it’s

quickly identified and blocked, both to halt spread and to remediate the Mac systems it’s

already gained a foothold on. XProtect adds to this defence, along with Gatekeeper and

Notarisation.

Finally, XProtect acts to remediate malware that has managed to successfully execute.

These protections, further described below, combine to support best-practice protection

from viruses and malware. There are additional protections, particularly on a Mac with

Apple silicon, to limit the potential damage of malware that does manage to execute. See

Protecting app access to user data for ways that macOS can help protect user data from

malware, and Operating system integrity for ways macOS can limit the actions malware can

take on the system.

Notarisation

Notarisation is a malware scanning service provided by Apple. Developers who want to

distribute apps for macOS outside the AppStore submit their apps for scanning as part

of the distribution process. Apple scans this software for known malware and, if none is

found, issues a Notarisation ticket. Typically, developers staple this ticket to their app so

Gatekeeper can verify and launch the app, even offline.

Apple can also issue a revocation ticket for apps known to be malicious — even if they’ve

been previously notarised. macOS regularly checks for new revocation tickets so that

Gatekeeper has the latest information and can block the launch of such files. This process

can very quickly block malicious apps because updates happen in the background much

more frequently than even the background updates that push new XProtect signatures. In

addition, this protection can be applied to both apps that have been previously and those

that haven’t.

106Apple Platform Security

XProtect

macOS includes built-in antivirus technology called XProtect for the signature-based

detection and removal of malware. The system uses YARA signatures, a tool used to

conduct signature-based detection of malware, which Apple updates regularly. Apple

monitors for new malware infections and strains, and updates signatures automatically—

independent from system updates — to help defend a Mac from malware infections.

XProtect automatically detects and blocks the execution of known malware. In macOS 10.15

or later, XProtect checks for known malicious content whenever:

• An app is first launched

• An app has been changed (in the file system)

• XProtect signatures are updated

When XProtect detects known malware, the software is blocked and the user is notified

and given the option to move the software to the Bin.

Note: Notarisation is effective against known files (or file hashes) and can be used on

apps that have been previously launched. The signature-based rules of XProtect are more

generic than a specific file hash, so it can find variants that Apple has not seen. XProtect

scans only apps that have been changed or apps at first launch.

Should malware make its way onto a Mac, XProtect also includes technology to remediate

infections. For example, it includes an engine that remediates infections based on updates

automatically delivered from Apple (as part of automatic updates of system data files

and security updates). It also removes malware upon receiving updated information, and

it continues to periodically check for infections. XProtect doesn’t automatically reboot

the Mac.

Automatic XProtect security updates

Apple issues the updates for XProtect automatically based on the latest threat intelligence

available. By default, macOS checks for these updates daily. Notarisation updates, which

are distributed using CloudKit sync, are much more frequent.

How Apple responds when new malware is discovered

When new malware is discovered, a number of steps may be performed:

• Any associated Developer ID certificates are revoked.

• Notarisation revocation tickets are issued for all files (apps and associated files).

• XProtect signatures are developed and released.

These signatures are also applied retroactively to previously notarised software, and

any new detections can result in one or more of the previous actions occurring.

Ultimately, a malware detection launches a series of steps over the next seconds, hours

and days that follow to propagate the best protections possible to Mac users.

107Apple Platform Security

Controlling app access to files in macOS

Apple believes that users should have full transparency, consent and control over what

apps are doing with their data. In macOS 10.15, this model is enforced by the system to

help ensure that all apps must obtain user consent before accessing files in Documents,

Downloads, Desktop, iCloud Drive and network volumes. In macOS 10.13 or later, apps that

require access to the full storage device must be explicitly added in System Preferences. In

addition, accessibility and automation capabilities require user permission to help ensure

they don’t circumvent other protections. Depending on the access policy, users may be

asked to, or be required to, change the setting in System Preferences > Security & Privacy >

Privacy:

Item User prompted by app User must edit system privacy

settings

Accessibility

Full internal storage access

Files and folders

Note: Includes Desktop, Documents,

Downloads, network volumes and

removable volumes

Automation (Apple events)

Items in the user’s Bin are protected from any apps that are using Full Disk Access; the

user won’t get prompted for app access. If the user wants apps to access the files, they

must be moved from the Bin to another location.

A user who turns on FileVault on a Mac is asked to provide valid credentials before

continuing the boot process and gaining access to specialised startup modes. Without

valid login credentials or a recovery key, the entire volume remains encrypted and is

protected from unauthorised access even if the physical storage device is removed and

connected to another computer.

To protect data in an enterprise setting, IT should define and enforce FileVault

configuration policies using mobile device management (MDM). Organisations have several

options for managing encrypted volumes, including institutional recovery keys, personal

recovery keys (that can optionally be stored with MDM for escrow) or a combination of

both. Key rotation can also be set as a policy in MDM.

108Apple Platform Security

Secure features in the Notes app

The Notes app includes a secure notes feature — on iPhone, iPad, Mac, and the iCloud

website — that allows users to protect the contents of specific notes. Users can also

securely share notes with others.

Secure notes

Secure notes are end-to-end encrypted using a user-provided passphrase that is required

to view the notes on iOS, iPadOS and macOS devices, and the iCloud website. Each iCloud

account (including “On my” device accounts) can have a separate passphrase.

When a user secures a note, a 16-byte key is derived from the user’s passphrase using

PBKDF2 and SHA256. The note and all of its attachments are encrypted using AES with

Galois/Counter Mode (AES-GCM). New records are created in Core Data and CloudKit to

store the encrypted note, attachments, tag and initialisation vector. After the new records

are created, the original unencrypted data is deleted. Attachments that support encryption

include images, sketches, tables, maps and websites. Notes containing other types of

attachments can’t be encrypted and unsupported attachments can’t be added to secure notes.

To view a secure note, the user must enter their passphrase or authenticate using FaceID

or TouchID. After successfully authenticating the user, whether to view or create a secure

note, Notes opens a secure session. While the secure session is open, the user can view or

secure other notes without additional authentication. However, the secure session applies

only to notes protected with the provided passphrase. The user still needs to authenticate

for notes protected by a different passphrase. The secure session is closed when:

• The user taps the Lock Now button in Notes

• Notes is switched to the background for more than 3 minutes (8 minutes in macOS)

• The iOS or iPadOS device locks

To change the passphrase on a secure note, the user must enter the current passphrase

because FaceID and TouchID aren’t available when changing the passphrase. After

choosing a new passphrase, the Notes app rewraps, in the same account, the keys of all

existing notes that are encrypted by the previous passphrase.

If a user mistypes the passphrase three times in a row, Notes shows a user-supplied hint if

one was provided by the user at setup. If the user still doesn’t remember their passphrase,

they can reset it in Notes settings. This feature allows users to create new secure

notes with a new passphrase but it won’t allow them to see previously secured notes.

The previously secured notes can still be viewed if the old passphrase is remembered.

Resetting the passphrase requires the user’s iCloud account passphrase.

Shared notes

Notes that aren’t end-to-end encrypted with a passphrase can be shared with others.

Shared notes still use the CloudKit encrypted data type for any text or attachments

that the user puts in a note. Assets are always encrypted with a key that’s encrypted in

the CKRecord. Metadata, such as the creation and modification dates, isn’t encrypted.

CloudKit manages the process by which participants can encrypt and decrypt each

other’s data.

109Apple Platform Security

Secure features in the Shortcuts app

In the Shortcuts app, shortcuts are optionally synced across Apple devices using iCloud.

Shortcuts can also be shared with other users through iCloud. Shortcuts are stored locally

in an encrypted format.

Custom shortcuts are versatile — they’re similar to scripts or programs. When downloading

shortcuts from the internet, the user is warned that the shortcut hasn’t been reviewed by

Apple and is given the opportunity to inspect the shortcut. To protect against malicious

shortcuts, updated malware definitions are downloaded to identify malicious shortcuts at

runtime.

Custom shortcuts can also run user-specified JavaScript on websites in Safari when

invoked from the share sheet. To protect against malicious JavaScript that, for example,

tricks the user into running a script on a social media website that harvests their data,

the JavaScript is validated against the aforementioned malware definitions. The first time

a user runs JavaScript on a domain, the user is prompted to allow shortcuts containing

JavaScript to run on the current web page for that domain.

110Apple Platform Security

Services security

Services security overview

Apple has built a robust set of services to help users get even more utility and productivity

out of their devices. These services provide powerful capabilities for cloud storage, sync,

password storage, authentication, payment, messaging, communications and more, all

while protecting users’ privacy and the security of their data.

This chapter covers security technologies used in iCloud, Sign in with Apple, ApplePay,

iMessage, Apple Messages for Business, FaceTime, Find My and Continuity.

Note: Not all Apple services and content are available in all countries or regions.

AppleID and Managed AppleID

AppleID security overview

An AppleID is the account used to sign in to Apple services. It’s important for users to

keep their AppleIDs secure to help prevent unauthorised access to their accounts. To help

with this, AppleIDs require strong passwords that:

• Must be at least eight characters in length

• Must contain both letters and numbers

• Must not contain three or more consecutive identical characters

• Can’t be a commonly used password

Users are encouraged to exceed these guidelines by adding extra characters and

punctuation marks to make their passwords even stronger.

Apple also notifies users by email or push notifications, or both, when important changes

are made to their account — for example, if a password or billing information has been

changed or the AppleID has been used to sign in on a new device. If anything looks

unfamiliar, users are instructed to change their AppleID password immediately.

In addition, Apple employs a variety of policies and procedures designed to protect user

accounts. These include limiting the number of retries for sign-in and password reset

attempts, active fraud monitoring to help identify attacks as they occur and regular policy

reviews that allow Apple to adapt to any new information that could affect user security.

Note: The Managed AppleID password policy is set by an administrator in Apple School

Manager or Apple Business Manager.

111Apple Platform Security

Two-factor authentication

To help users further secure their accounts, by default Apple uses two-factor

authentication — an extra layer of security for AppleIDs. It’s designed to ensure that only

the account’s owner can access the account, even if someone else knows the password.

With two-factor authentication, a user’s account can be accessed on only trusted devices,

such as the user’s iPhone, iPad, iPodtouch or Mac, or on other devices after completing

a verification from one of these trusted devices or a trusted phone number. To sign in for

the first time on any new device, two pieces of information are required — the AppleID

password and a six-digit verification code that’s displayed on the user’s trusted devices

or sent to a trusted phone number. By entering the code, the user confirms that they trust

the new device and that it’s safe to sign in. Because a password alone is no longer enough

to access a user’s account, two-factor authentication improves the security of the user’s

AppleID and all the personal information they store with Apple. It’s integrated directly

into iOS, iPadOS, macOS, tvOS, watchOS and the authentication systems used by Apple

websites.

When a user signs in to an Apple website using a web browser, a second factor request is

sent to all trusted devices associated with the user’s iCloud account, requesting approval

of the web session. If the user is signing in to an Apple website from a browser on a trusted

device, they see the verification code displayed locally on the device they’re using. When

the user enters the code on that device, the web session is approved.

Password reset and account recovery

If an AppleID account password is forgotten, a user can reset it on a trusted device. If a

trusted device isn’t available and the password is known, a user can use a trusted phone

number can be used to authenticate through SMS verification. In addition, to provide

immediate recovery for an AppleID, a previously used passcode can be used to reset

in conjunction with SMS. If these options aren’t possible, the account recovery process

must be followed. For more information, see the Apple Support article How to use account

recovery when you can’t reset your AppleID password.

Managed AppleID security

Managed AppleIDs function much like an AppleID but are owned and controlled by

enterprise or educational organisations. These organisations can reset passwords, limit

purchasing and communications such as FaceTime and Messages, and set up role-based

permissions for employees, staff members, teachers and students.

For Managed AppleIDs, some services are disabled (for example, ApplePay, iCloud

Keychain, HomeKit and Find My).

Inspecting Managed AppleIDs

Managed AppleIDs also support inspection, which allows organisations to comply with

legal and privacy regulations. An Apple School Manager administrator, manager or teacher

can inspect specific Managed AppleID accounts.

Inspectors can only monitor accounts that are below them in the organisation’s hierarchy.

For example, teachers can monitor students, managers can inspect teachers and students,

and administrators can inspect managers, teachers and students.

112Apple Platform Security

When inspecting credentials are requested using Apple School Manager, a special

account is issued that has access to only the Managed AppleID for which inspecting was

requested. The inspector can then read and modify the user’s content stored in iCloud

or in CloudKit-enabled apps. Every request for auditing access is logged in Apple School

Manager. The logs show who the inspector was, the Managed AppleID the inspector

requested access to, the time of the request and whether the inspection was performed.

Managed AppleIDs and personal devices

Managed AppleIDs can also be used with personally owned iOS and iPadOS devices and

Mac computers. Students sign in to iCloud using the Managed AppleID issued by the

institution and an additional home-use password, which serves as the second factor of the

AppleID two-factor authentication process. While students are using a Managed AppleID

on a personal device, iCloud Keychain isn’t available, and the institution might restrict

other features such as FaceTime or Messages. Any iCloud documents created by students

when they are signed in are subject to audit as described previously in this section.

iCloud

iCloud security overview

iCloud stores a user’s contacts, calendars, photos, documents and more and keeps the

information up to date across all their devices automatically. iCloud can also be used

by third-party apps to store and sync documents as well as key values for app data as

defined by the developer. Users set up iCloud by signing in with an AppleID and choosing

which services they would like to use. Certain iCloud features, such as iCloud Drive and

iCloud Backup, can be disabled by IT administrators using mobile device management

(MDM) configuration profiles.

iCloud uses strong security methods and employs strict policies to protect user data. Most

iCloud data is first encrypted on the user’s device, using device-generated iCloud keys,

before being uploaded to iCloud servers. For data that isn’t end-to-end encrypted, the

user’s device securely uploads these iCloud keys to iCloud Hardware Security Modules

in Apple data centres. This allows Apple to help the user with data recovery and decrypt

the data on the user’s behalf whenever they need it (for example, when they sign in on a

new device, restore from a backup or access their iCloud data on the web). Data moving

between the user’s devices and iCloud servers is separately encrypted in transit with TLS,

and iCloud servers store user data with an additional layer of encryption at rest.

Encryption keys, when available to Apple, are secured in Apple data centres. When

processing data stored in a third-party data centre, these encryption keys are accessed

only by Apple software in use on secure servers, and only while conducting the necessary

processing. For additional privacy and security, many Apple services use end-to-end

encryption, which means the user’s iCloud data can be accessed only by the users

themselves, and only from the trusted devices where they are signed in with their AppleID.

113Apple Platform Security

Apple offers users two options to encrypt and protect the data they store in iCloud:

• Standard data protection (the default setting): The user’s iCloud data is encrypted,

the encryption keys are secured in Apple data centres, and Apple can assist with data

and account recovery. Only certain iCloud data — 14 data categories, including Health

data and passwords in iCloud Keychain — is end-to-end encrypted.

• Advanced Data Protection for iCloud: An optional setting that offers Apple’s highest

level of cloud data security. If a user chooses to turn on Advanced Data Protection, their

trusted devices retain sole access to the encryption keys for the majority of their iCloud

data, thereby protecting it using end-to-end encryption. When you turn on Advanced

Data Protection, the number of data categories that use end-to-end encryption rises to

23 and includes your iCloud Backup, Photos, Notes and more.

The specific categories of iCloud data protected with end-to-end encryption are listed in

the Apple Support article iCloud data security overview.

iCloud encryption

Data encryption in iCloud is closely tied to the data storage model, starting with the

CloudKit frameworks and APIs that allow apps and system software to store data in iCloud

on behalf of the user, and keep everything up to date across devices and on the web.

CloudKit encryption

CloudKit is a framework that lets app developers store key-value data, structured data

and assets (large data stored separately from the database, such as images or videos) in

iCloud. CloudKit supports both public and private databases, grouped in containers. Public

databases are globally shared, typically used for generic assets, and aren’t encrypted.

Private databases store each user’s iCloud data.

CloudKit uses a hierarchy of keys that matches the structure of the data. Each container’s

private database is protected by a key hierarchy, rooted in an asymmetric key called a

CloudKit Service key. These keys are unique to each iCloud user and generated on their

trusted device. When data is written to CloudKit, all record keys are generated on the user’s

trusted device and wrapped to the appropriate key hierarchy before any data is uploaded.

Many Apple services, listed in the Apple Support article iCloud data security overview, use

end-to-end encryption with a CloudKit service key protected by iCloud Keychain syncing.

For these CloudKit containers, the service keys are stored in the user’s iCloud Keychain

and share the security characteristics of iCloud Keychain; the service keys are available

only on the user’s trusted devices, and can’t be accessed by Apple or any third party. In

the event of device loss, users can recover their iCloud Keychain data through the use of

Secure iCloud Keychain recovery, Account Recovery Contacts or an Account Recovery Key.

114Apple Platform Security

Encryption key management

The security of encrypted data in CloudKit relies on the security of the corresponding

encryption keys. CloudKit service keys are divided into two categories: end-to-end

encrypted and available-after-authentication.

• End-to-end encrypted service keys: For end-to-end encrypted iCloud services,

the relevant CloudKit service private keys are never made available to Apple servers.

Service key pairs, including the private keys, are created locally on a user’s trusted

device and transferred to the user’s other devices using iCloud Keychain security.

Although iCloud Keychain recovery and synchronisation flows are mediated by Apple

servers, these servers are cryptographically prevented from accessing any of the user’s

keychain data. In the worst case of losing access to iCloud Keychain and all its recovery

mechanisms, the end-to-end encrypted data in CloudKit is lost. Apple can’t help

recover this data.

• Available-after-authentication service keys: For other services, such as Photos and

iCloud Drive, the service keys are stored in iCloud Hardware Security Modules in Apple

data centres, and can be accessed by some Apple services. When a user signs in to

iCloud on a new device and authenticates their AppleID, these keys can be accessed by

Apple servers without further user interaction or input. For example, after signing in to

iCloud.com, the user can immediately view their photos online. These service keys are

available-after-authentication keys.

Advanced Data Protection for iCloud

Advanced Data Protection for iCloud is an optional setting that offers Apple’s highest

level of cloud data security. When a user turns on Advanced Data Protection, their trusted

devices retain sole access to the encryption keys for the majority of their iCloud data,

thereby protecting it with end-to-end encryption. For users who turn on Advanced Data

Protection, the total number of data categories protected using end-to-end encryption

rises from 14 to 23 and includes iCloud Backup, Photos, Notes and more.

Advanced Data Protection for iCloud will be available to US users by the end of 2022 and

will start rolling out to the rest of the world in early 2023.

Conceptually, Advanced Data Protection is simple: All CloudKit Service keys that were

generated on device and later uploaded to the available-after-authentication iCloud

Hardware Security Modules (HSMs) in Apple data centres are deleted from those HSMs

and instead kept entirely within the account’s iCloud Keychain protection domain. They are

handled like the existing end-to-end encrypted service keys, which means Apple can no

longer read or access these keys.

Advanced Data Protection also automatically protects CloudKit fields that third-party

developers choose to mark as encrypted, and all CloudKit assets.

115Apple Platform Security

Enabling Advanced Data Protection

When the user turns on Advanced Data Protection, their trusted device performs two

actions: First, it communicates the user’s intent to turn on Advanced Data Protection to

their other devices that participate in end-to-end-encryption. It does so by writing a new

value, signed by device-local keys, into its iCloud Keychain device metadata. Apple servers

can’t remove or modify this attestation while it gets synchronised with the user’s other

devices.

Second, the device initiates the removal of the available-after-authentication service keys

from Apple data centres. As these keys are protected by iCloud HSMs, this deletion is

immediate, permanent and irrevocable. After the keys are deleted, Apple can no longer

access any of the data protected by the user’s service keys. At this time, the device

begins an asynchronous key rotation operation, which creates a new service key for each

service whose key was previously available to Apple servers. If the key rotation fails, due

to network interruption or any other error, the device retries the key rotation until it’s

successful.

After the service key rotation is successful, new data written to the service can’t be

decrypted with the old service key. It’s protected with the new key, which is controlled

solely by the user’s trusted devices, and was never available to Apple.

Advanced Data Protection and iCloud.com web access

When a user first turns on Advanced Data Protection, web access to their data at iCloud.

com is automatically turned off. This is because iCloud web servers no longer have access

to the keys required to decrypt and display the user’s data. The user can choose to turn

on web access again, and use the participation of their trusted device to access their

encrypted iCloud data on the web.

After turning on web access, the user must authorise the web sign-in on one of their

trusted devices each time they visit iCloud.com. The authorisation “arms” the device for

web access. For the next hour, this device accepts requests from specific Apple servers

to upload individual service keys, but only those corresponding to an allow list of services

normally accessible on iCloud.com. In other words, even after the user authorises a web

sign-in, a server request is unable to induce the user’s device to upload service keys for

data that isn’t intended to be viewed on iCloud.com (such as Health data or passwords

in iCloud Keychain). Apple servers request only the service keys needed to decrypt the

specific data the user is requesting to access on the web. Every time a service key is

uploaded, it is encrypted using an ephemeral key bound to the web session that the user

authorised, and a notification is displayed on the user’s device, showing the iCloud service

whose data is temporarily being made available to Apple servers.

Preserving the user’s choices

The Advanced Data Protection and iCloud.com web access settings can be modified only

by the user. These values are stored in the user’s iCloud Keychain device metadata and can

only be changed from one of the user’s trusted devices. Apple servers can’t modify these

settings on behalf of the user, nor can they roll them back to a previous configuration.

116Apple Platform Security

Security implications of sharing and collaboration

In most cases, when users share content to collaborate with each other — for example, with

shared Notes, shared Reminders, shared folders in iCloud Drive or iCloud Shared Photo

Library — and all the users have Advanced Data Protection turned on, Apple servers are

used only to establish sharing, but don’t have access to the encryption keys for the shared

data. The content remains end-to-end encrypted and accessible only on participants’

trusted devices. For each sharing operation, a title and representative thumbnail may be

stored by Apple with standard data protection to show a preview to the receiving users.

Selecting the “anyone with a link” option when enabling collaboration will make the content

available to Apple servers under standard data protection, as the servers need to be able

to provide access to anyone who opens the URL.

iWork collaboration and the Shared Albums feature in Photos don’t support Advanced Data

Protection. When users collaborate on an iWork document, or open an iWork document

from a shared folder in iCloud Drive, the encryption keys for the document are securely

uploaded to iWork servers in Apple data centres. This is because real-time collaboration

in iWork requires server-side mediation to coordinate document changes between

participants. Photos added to Shared Albums are stored with standard data protection as

the feature permits albums to be publicly shared on the web.

Disabling Advanced Data Protection

The user can turn off Advanced Data Protection at any time. If they decide to do so:

1. The user’s device first records their new choice in iCloud Keychain participation

metadata, and this setting is securely synchronised to all their devices.

2. The user’s device securely uploads the service keys for all available-after-authentication

services to the iCloud HSMs in Apple data centres. This never includes keys for services

that are end-to-end encrypted under standard data protection, such as iCloud Keychain

and Health.

The device uploads both the original service keys, generated before Advanced Data

Protection had been turned on, and the new service keys that were generated after

the user turned on the feature. This makes all data in these services accessible after

authentication and returns the account to standard data protection, where Apple can once

again help the user recover most of their data should they lose access to their account.

iCloud data not covered by Advanced Data Protection

Because of the need to interoperate with the global email, contacts and calendar systems,

iCloud Mail, Contacts and Calendar aren’t end-to-end encrypted.

iCloud stores some data without the protection of user-specific CloudKit service keys, even

when Advanced Data Protection is turned on. CloudKit Record fields must be explicitly

declared as “encrypted” in the container’s schema to be protected, and reading and writing

encrypted fields requires the use of dedicated APIs. Dates and times when a file or object

was modified are used to sort a user’s information, and checksums of file and photo data

are used to help Apple de-duplicate and optimise the user’s iCloud and device storage —

all without having access to the files and photos themselves. Details about how encryption

is used for specific data categories is available in the Apple Support article iCloud data

security overview.

117Apple Platform Security

Decisions such as the use of checksums for data de-duplication — a well-known technique

called convergent encryption — were part of the original design of iCloud services when

they launched. This metadata is always encrypted, but the encryption keys are stored by

Apple with standard data protection. To continue to strengthen security protections for all

users, Apple is committed to ensuring more data, including this kind of metadata, is end-

to-end encrypted when Advanced Data Protection is turned on.

Advanced Data Protection requirements

The requirements to turn on Advanced Data Protection for iCloud include the following:

• The user’s account must support end-to-end encryption. End-to-end encryption

requires two-factor authentication for their AppleID and a passcode or password set on

their trusted devices. For more information, see the Apple Support article Two-factor

authentication for AppleID.

• Devices where the user is signed in with their AppleID must be updated to iOS 16.2,

iPadOS 16.2, macOS 13.1, tvOS 16.2, watchOS 9.2, and the latest version of iCloud for

Windows. This requirement prevents a previous version of iOS, iPadOS, macOS, tvOS or

watchOS from mishandling the newly created service keys by re-uploading them to the

available-after-authentication HSMs in a misguided attempt to repair the account state.

• The user must set up at least one alternative recovery method — one or more recovery

contacts or a recovery key — which they can use to recover their iCloud data if they lose

access to their account.

If the recovery methods fail, such as if the recovery contact’s information is out of date,

or the user forgets them, Apple can’t help recover the user’s end-to-end encrypted

iCloud data.

Advanced Data Protection for iCloud can be turned on only for AppleIDs.

Managed AppleIDs and child accounts (varies by country or region) aren’t supported.

Security of iCloud Backup

iCloud backs up information — including device settings, app data, photos and videos in

the Camera Roll, and conversations in the Messages app — daily over Wi-Fi. iCloud Backup

occurs only when the device is locked, connected to a power source and has Wi-Fi access

to the internet. Mindful of the storage encryption used in iOS and iPadOS, iCloud Backup

is designed to keep data secure while allowing incremental, unattended backup and

restoration to occur. By default, the iCloud Backup service key is securely backed up to

iCloud Hardware Security Modules in Apple data centres, and is part of the available-after-

authentication data category. For users who turn on Advanced Data Protection for iCloud,

the iCloud Backup service key is protected with end-to-end encryption and available only

to users on their trusted devices.

When files are created in Data Protection classes that aren’t accessible when the

device is locked, their per-file keys are encrypted using the class keys from the

iCloud Backupkeybag and backing the files up to iCloud in their original, encrypted state.

All files are encrypted during transport and, when stored, encrypted using account-based

keys as described in CloudKit encryption.

118Apple Platform Security

The iCloud Backup keybag contains asymmetric (Curve25519) keys for Data Protection

classes that aren’t accessible when the device is locked. The backup set is stored in the

user’s iCloud account and consists of a copy of the user’s files and the iCloud Backup

keybag. The iCloud Backup keybag is protected by a random key, which is also stored with

the backup set. The user’s iCloud password isn’t used for encryption, so changing the

iCloud password won’t invalidate existing backups.

On restore, the backed-up files, iCloud Backup keybag and the key for the keybag are

retrieved from the user’s iCloud account. The iCloud Backup keybag is decrypted using

its key, then the per-file keys in the keybag are used to decrypt the files in the backup set,

which are written as new files to the file system, thus re-encrypting them according to their

Data Protection class.

The following content is backed up using iCloud Backup:

• Records for purchased music, movies, TV shows, apps and books. A user’s

iCloud Backup includes information about purchased content present on the

user’s device, but not the purchased content itself. When the user restores from

an iCloud Backup, their purchased content is automatically downloaded from the

iTunesStore, the AppStore, the AppleTV app or Apple Books. Some types of content

aren’t downloaded automatically in all countries or regions, and previous purchases may

be unavailable if they have been refunded or are no longer available in their respective

store. Full purchase history is associated with a user’s AppleID.

• Photos and videos on a user’s devices. Note that if a user turns on iCloud Photos in

iOS8.1, iPadOS13.1 or OSX10.10.3, or later, their photos and videos are already stored

in iCloud, so they aren’t included in the user’s iCloud Backup.

• Contacts, calendar events, reminders and notes

• Device settings

• App data

• Home Screen and app organisation

• HomeKit configuration

• Medical ID data

• Voice Memos password (if necessary; requires the physical SIM card that was in use

during backup)

• Message, Apple Messages for Business, text (SMS) and MMS messages (if necessary;

requires the physical SIM card that was in use during backup)

iCloud Backup is also used to back up the local device keychain, encrypted with a key

derived from the Secure Enclave UID root cryptographic key of the device. This key is

unique to the device and not known to Apple. This allows the database to be restored only

to the same device from which it originated, and it means no one else, including Apple, can

read it. For more information, see Secure Enclave.

119Apple Platform Security

Messages in iCloud

Messages in iCloud keeps a user’s entire message history updated and available on all

devices.

With standard data protection, Messages in iCloud is end-to-end encrypted when

iCloud Backup is turned off. When iCloud Backup is turned on, the backup includes a

copy of the Messages in iCloud encryption key so Apple can help the user recover their

messages even if they have lost access to iCloud Keychain and their trusted devices. If

the user turns off iCloud Backup, a new key is generated on their device to protect future

Messages in iCloud. The new key is stored only in iCloud Keychain, only accessible to the

user on their trusted devices, and new data written to the container can’t be decrypted

with the old container key.

With Advanced Data Protection, Messages in iCloud is always end-to-end encrypted. When

iCloud Backup is turned on, everything inside it is end-to-end encrypted, including the

Messages in iCloud encryption key. The iCloud Backup service key, as well as the Messages

in iCloud container key, are both rolled when the user turns on Advanced Data Protection.

For more information, see the Apple Support article iCloud data security overview.

Account recovery contact security

Users can add up to five people they trust as account recovery contacts to help them

recover their iCloud account and data, including all their end-to-end encrypted data,

whether or not they have turned on Advanced Data Protection. Neither Apple nor the

recovery contact have the necessary information individually to recover the user’s end-to-

end encrypted iCloud data.

Recovery Contact is designed with user privacy in mind. A user’s chosen recovery contacts

aren’t known to Apple. Apple servers only learn information about a recovery contact

late in the course of a recovery attempt after the user asks the contact for help and their

contact begins actually assisting with the recovery. That information isn’t retained after the

recovery completes.

Recovery contact security process

When a user sets up an Account Recovery Contact, the key to access the user’s iCloud

data — including end-to-end encrypted CloudKit data — is encrypted with a strong random

key. This random key is then split between the recovery contact and Apple. At recovery

time, only when the two key shares are recombined can the original key be recovered and

the user’s iCloud data accessed.

To set up an Account Recovery Contact, the user’s device communicates with Apple

servers to upload the share of the keying information Apple will hold. It then establishes an

end-to-end encrypted CloudKit container with the recovery contact to share the portion

the recovery contact needs. Both Apple and the recovery contact also receive the same

authorisation secret from the user, which is needed later for recovery. The communication

to invite and accept recovery contacts takes places through a mutually authenticated IDS

channel. The recovery contact automatically stores the received information in their iCloud

Keychain. Apple can’t access either the contents of the CloudKit container or the iCloud

Keychain that stores this information. When the sharing is performed, Apple servers view

only an anonymous ID for the recovery contact.

120Apple Platform Security

Later, when a user needs to recover their account and iCloud data, they can request help

from their recovery contact. At that time, a recovery code is generated by the recovery

contact’s device, which the recovery contact then provides to the user via a different

method (for example, in person or over the phone). The user then enters the recovery

code on their device to establish a secure connection between devices using the SPAKE2+

protocol, the contents of which aren’t accessible by Apple. This interaction is orchestrated

by Apple servers, but Apple can’t initiate the recovery process.

After the secure connection is established and all required security checks are completed,

the recovery contact’s device returns their portion of the keying information and the

previously established authorisation secret back to the user requesting recovery. The

user presents this authorisation secret to an Apple server, which grants access to the

keying information Apple is keeping. Providing the authorisation secret also authorises the

account password reset to restore account access.

Finally, the user’s device recombines the keying information received from Apple and the

Account Recovery Contact, and then uses it to decrypt and recover their iCloud data.

There are safeguards in place to prevent a recovery contact from initiating recovery

without the user’s consent, which include a liveness check on the user’s account. If the

account is in active use, recovery using a recovery contact also requires knowledge of a

recent device passcode or the iCloud Security Code.

Legacy Contact security

If a user wants their iCloud data to be accessible to designated beneficiaries after their

death, they can set up Legacy Contacts on their account. A Legacy Contact beneficiary

gains access to all the deceased’s iCloud data, including almost all end-to-end encrypted

data, but excluding iCloud Keychain data like account passwords. The technology

underlying Legacy Contact is similar to how Recovery Contact works — a strong random

key that is split between Apple and the legacy contact, so that neither can decrypt any

data by themselves. A beneficiary receives the same classes of data whether or not the

user turned on Advanced Data Protection.

The keying information a beneficiary receives is referred to as an access key in user-facing

documentation, and is saved automatically on supported devices, but can also be printed

and stored offline for use. For more information, see the Apple Support article How to add

a Legacy Contact for your AppleID.

After the user’s death, Legacy Contacts sign in to the Apple claim website to initiate

access. This requires a death certificate and is authorised in part with the authorisation

secret mentioned in the previous section. After all the security checks are completed,

Apple issues a username and password for the new account and releases the necessary

keying information to the Legacy Contact.

To more easily input the access key when needed, it’s presented as an alphanumeric code

with an associated QR code. After it’s entered, access to the deceased’s iCloud data is

restored. This can be performed on a device or access can be established online. For more

information, see the Apple Support article Request access to an Apple account as a Legacy

Contact.

121Apple Platform Security

iCloud Private Relay security

iCloud Private Relay helps protect users primarily when browsing the web with Safari,

but it also includes all DNS name resolution requests. This helps ensure that no single

party, not even Apple, can correlate the user’s IP address with their browsing activity. It

does this by using different proxies — an ingress proxy managed by Apple, and an egress

proxy managed by a content provider. To use iCloud Private Relay, the user must be using

iOS 15, iPadOS15 or macOS 12.0.1, or later, and be signed in to their iCloud+ account with

their AppleID. iCloud Private Relay can then be turned on in Settings > iCloud or System

Settings > iCloud.

For more information, see iCloud Private Relay Overview.

Passcode and password management

Password security overview

iOS, iPadOS and macOS make it easy for users to authenticate to third-party apps and

websites that use passwords. The best way to manage passwords is not to have to use

one. Sign in with Apple lets users sign in to third-party apps and websites without having

to create and manage an additional account or password, while protecting the sign-in with

their two-factor authentication for AppleID. For sites that don’t support Sign in with Apple,

the Automatic Strong Password feature enables a user’s devices to automatically create,

sync and enter unique strong passwords for sites and apps. In iOS and iPadOS, passwords

are saved to a special Password AutoFill keychain that’s user controlled and manageable by

going to Settings > Passwords.

In macOS, saved passwords can be managed in Safari Passwords preferences. This sync

system can also be used to sync passwords that are manually created by the user.

provides the convenience and efficiency of one-tap sign-in while giving the user more

transparency and control over their personal information.

using the AppleID they already have and it gives them more control over their personal

information. Apps can only ask for the user’s name and email address when setting up an

account, and the user always has a choice: They can share their personal email address

with an app or choose to keep their personal email private and use the new Apple private

email relay service instead. This email relay service shares a unique, anonymised email

address that forwards to the user’s personal address so they can still receive useful

communication from the developer while maintaining a degree of privacy and control over

their personal information.

two-factor authentication enabled for their AppleID. Two-factor authentication helps

secure not only the user’s AppleID but also the accounts they establish with their apps.

Furthermore, Apple has developed and integrated a privacy-friendly anti-fraud signal into

are real people and not bots or scripted accounts.

122Apple Platform Security

Automatic strong passwords

When iCloud Keychain is enabled, iOS, iPadOS and macOS create strong, random, unique

passwords when users sign up for or change their password on a website in Safari. In iOS

and iPadOS, automatic strong password generation is also available in apps. Users must

opt out of using strong passwords. Generated passwords are saved in the keychain and

kept up to date across devices with iCloud Keychain, when it’s enabled.

By default, passwords generated by iOS and iPadOS are 20 characters long. They contain

one digit, one uppercase character, two hyphens and 16 lowercase characters. These

generated passwords are strong, containing 71 bits of entropy.

Passwords are generated based on heuristics that determine whether a password-field

experience is for password creation. If the heuristic fails to recognise a context-specific

password being used at password creation, app developers can set UITextContentType.

newPassword on their text field and web developers can set autocomplete= “new-

password” on their <input> elements.

To help ensure that generated passwords are compatible with the relevant services,

apps and websites can provide rules. Developers provide these rules using

UITextInputPasswordRules or the passwordrules attribute on their input elements.

Devices then generate the strongest password they can that fulfils these rules.

Password AutoFill security

Password AutoFill automatically fills credentials stored in the keychain. The iCloud

Keychain password manager and Password AutoFill provide the following features:

• Filling in credentials in apps and websites

• Generating strong passwords

• Saving passwords in both apps and websites in Safari

• Sharing passwords securely to a users’ contacts

• Providing passwords to a nearby AppleTV that’s requesting credentials

Generating and saving passwords within apps, as well as providing passwords to AppleTV,

are available only in iOS and iPadOS.

Password AutoFill in apps

iOS and iPadOS allow users to input saved usernames and passwords into credential-

related fields in apps, similarly to the way Password AutoFill works in Safari. In iOS and

iPadOS, users tap a key affordance in the software keyboard’s QuickType bar. In macOS,

for apps built with Mac Catalyst, a Passwords drop-down menu appears below credential-

related fields.

When an app is strongly associated with a website that uses the same app-website

association mechanism and that’s powered by the same apple-app-site-association

file, the iOS and iPadOS QuickType bar and macOS drop-down menu directly suggest

credentials for the app, if any are saved to the Password AutoFill Keychain. This allows

users to choose to disclose Safari-saved credentials to apps with the same security

properties, without those apps having to adopt an API.

123Apple Platform Security

Password AutoFill exposes no credential information to an app until a user consents to release a

credential to the app. The credential lists are drawn from or presented out of the app’s process.

When an app and website have a trusted relationship and a user submits credentials within

an app, iOS and iPadOS may prompt the user to save those credentials to the Password

AutoFill keychain for later use.

App access to saved passwords

iOS, iPadOS and macOS apps can request the Password AutoFill keychain’s help with signing

a user in using ASAuthorizationPasswordProvider and SecAddSharedWebCredential.

The password provider and their request can be used in conjunction with Sign in with Apple,

so that the same API is called to help users sign in to an app, regardless of whether the user’s

account is password based or was created using Sign in with Apple.

Apps can access saved passwords only if the app developer and website administrator

have given their approval and the user has given consent. App developers express their

intent to access Safari-saved passwords by including an entitlement in their app. The

entitlement lists the fully qualified domain names of associated websites, and the websites

must place a file on their server listing the unique app identifiers of apps approved by Apple.

When an app with the com.apple.developer.associated-domains entitlement is installed, iOS

and iPadOS make a TLS request to each listed website, requesting one of the following files:

• apple-app-site-association

• .well-known/apple-app-site-association

If the file lists the app identifier of the app being installed then iOS and iPadOS mark the

website and app as having a trusted relationship. Only with a trusted relationship will calls

to these two APIs result in a prompt to the user, who must agree before any passwords are

released to the app, updated or deleted.

Password security recommendations

The Password AutoFill passwords list in iOS, iPadOS and macOS indicates which of a user’s

saved passwords will be reused with other websites, passwords that are considered weak

and passwords that have been compromised by a data leak.

Overview

Using the same password for more than one service may leave those accounts vulnerable

to a credential-stuffing attack. If a service is breached and passwords are leaked, attackers

may try the same credentials on other services to compromise additional accounts.

• Passwords are marked reused if the same password is seen used for more than one

saved password across different domains.

• Passwords are marked weak if they may be easily guessed by an attacker. iOS, iPadOS,

and macOS detect common patterns used to create memorable passwords, such as

using words found in a dictionary, common character substitutions (such as using

“p4ssw0rd” instead of “password”), patterns found on a keyboard (such as “q12we34r”

from a QWERTY keyboard), or repeated sequences (such as “123123”). These patterns

are often used to create passwords that satisfy minimum password requirements for

services but are also commonly used by attackers attempting to obtain a password

using brute force.

124Apple Platform Security

Because many services specifically require a four- or six-digit PIN code, these short

passcodes are evaluated with different rules. PIN codes are considered weak if they are

one of the most common PIN codes, if they are an increasing or decreasing sequence

such as “1234” or “8765”, or if they follow a repetition pattern such as “123123” or

“123321”.

• Passwords are marked leaked if the Password Monitoring feature can claim they have

been present in a data leak. For more information, see Password Monitoring.

Weak, reused and leaked passwords are either indicated in the list of passwords (macOS)

or present in the dedicated Security Recommendations interface (iOS and iPadOS). If the

user logs in to a website in Safari using a previously saved password that’s very weak or

that’s been compromised by a data leak, they’re shown an alert strongly encouraging them

to upgrade to an automatic strong password.

Upgrading account authentication security in iOS and iPadOS

Apps that implement an Account Authentication Modification Extension (in the

Authentication Services framework) can provide easy, tap-of-a-button upgrades for

password-based accounts — namely, they can switch to using Sign in with Apple or an

automatic strong password. This extension point is available in iOS and iPadOS.

If an app has implemented the extension point and is installed on device, users see

extension upgrade options when viewing Security Recommendations for credentials

associated with the app in the iCloud Keychain password manager in Settings. The

upgrades are also offered when users sign in to the app with the at-risk credential. Apps

have the ability to tell the system not to prompt users with upgrade options after signing in.

Using new AuthenticationServices API, apps can also invoke their extensions and perform

upgrades themselves, ideally from an account settings or account management screen in

the app.

Apps can choose to support strong password upgrades, Sign in with Apple upgrades or

both. In a strong password upgrade, the system generates an automatic strong password

for the user. If necessary, the app can provide custom password rules to follow when

generating the new password. When a user switches an account from using a password to

using Sign in with Apple, the system provides a new Sign in with Apple credential to the

extension to associate the account with. The user’s AppleID email isn’t provided as part

of the credential. After a successful Sign in with Apple upgrade, the system deletes the

previously used password credential from the user’s keychain if it’s saved there.

Account Authentication Modification Extensions have the opportunity to perform additional

user authentication before performing an upgrade. For upgrades initiated within the

password manager or after signing in to an app, the extension provides the username and

password for the account to upgrade. For in-app upgrades, only the username is provided.

If the extension requires further user authentication, it can request to show a custom user

interface before moving on with the upgrade. The intended use case for showing this

user interface is to have the user enter a second factor of authentication to authorise the

upgrade.

125Apple Platform Security

Password Monitoring

Password Monitoring is a feature that matches passwords stored in the user’s Password

AutoFill keychain against a continuously updated and curated list of passwords known to

have been exposed in leaks from different online organisations. If the feature is turned

on, the monitoring protocol continuously matches the user’s Password AutoFill keychain

passwords against the curated list.

How monitoring works

The user’s device continuously performs round-robin checks on a user’s passwords,

querying an interval that’s independent of the user’s passwords or their password manager

usage patterns. This helps ensure that verification states remain up to date with the

current curated list of leaked passwords. To help prevent leakage of information related to

how many unique passwords a user has, requests are batched and performed in parallel.

A fixed number of passwords are verified in parallel on each check, and if a user has fewer

than this number, random passwords are generated and added to the queries to make up

the difference.

How passwords are matched

Passwords are matched in a two-part process. The most commonly leaked passwords are

contained within a local list on the user’s device. If the user’s password occurs on this list,

the user is immediately notified without any external interaction. This is designed to ensure

that no information is leaked about the passwords a user has that are most at risk due to a

password breach.

If the password isn’t contained on the most frequent list, it’s matched against less

frequently leaked passwords.

Comparing users’ passwords against a curated list

To verify whether a password not present in the local list is a match involves some

interaction with Apple servers. To help ensure that legitimate users’ passwords aren’t sent

to Apple, a form of cryptographic private set intersection is deployed that compares the

users’ passwords against a large set of leaked passwords. This is designed to ensure that

for passwords less at risk of breach, little information is shared with Apple. For a user’s

password, this information is limited to a 15-bit prefix of a cryptographic hash. The removal

of the most frequently leaked passwords from this interactive process, using the local list of

most commonly leaked passwords, reduces the delta in relative frequency of passwords in

the web services buckets, making it impractical to infer user passwords from these lookups.

The underlying protocol partitions the list of curated passwords, which contained

approximately 1.5 billion passwords at the time of writing, into 215 different buckets. The

bucket a password belongs to is based on the first 15 bits of the SHA256 hash value of

the password. Additionally, each leaked password, pw, is associated with an elliptic curve

point on the NIST P256 curve: Ppw = ⍺·HSWU(pw), where ⍺ is a secret random key known

only to Apple and HSWU is a random oracle function that maps passwords to curve points

based on the Shallue-van de Woestijne-Ulas method. This transformation is designed to

computationally hide the values of passwords and helps prevent revealing newly leaked

passwords through Password Monitoring.

126Apple Platform Security

To compute the private set intersection, the user’s device determines the bucket the user’s

password belongs to using λ, the 15-bit prefix of SHA256(upw), where upw is one of the

user’s passwords. The device generates their own random constant, β and sends the point

Pc = β·HSWU(upw) to the server, along with a request for the bucket corresponding to λ.

Here β hides information about the user’s password and limits to λ the information exposed

from the password to Apple. Finally, the server takes the point sent by the user’s device,

computes ⍺Pc = ⍺β·HSWU(upw), and returns it, along with the appropriate bucket of points —

Bλ = { Ppw | SHA256(pw) begins with prefix λ} — to the device.

The returned information allows the device to compute B’λ = {β·Ppw | Ppw ∈ Bλ}, and

ascertains that the user’s password has been leaked if ⍺Pc ∈ B'λ.

Sending passwords to other users or Apple devices

Apple sends passwords securely to other users or Apple devices with AirDrop and on

AppleTV.

Saving credentials to another device with AirDrop

When iCloud is enabled, users can use AirDrop to send a saved credential to another

device. The credential includes the user’s name and password and the websites it’s saved

for. Sending credentials with AirDrop always operates in Contacts Only mode, regardless of

the user’s settings. On the receiving device, after user consent, the credentials are stored

in the user’s Password AutoFill Keychain.

Filling in credentials in apps on AppleTV

Password AutoFill is available to fill credentials in apps on AppleTV. When the user focuses

on a username or password text field in tvOS, AppleTV begins advertising a request for

Password AutoFill over Bluetooth Low Energy (BLE).

Any nearby iPhone, iPad or iPodtouch displays a prompt inviting the user to share a

credential with AppleTV. Here’s how the encryption method is established:

• If the device and AppleTV use the same iCloud account, encryption between the

devices happens automatically.

• If the device is signed in to an iCloud account other than the one used by AppleTV,

the user is prompted to establish an encrypted connection through use of a PIN code.

To receive this prompt, the iPhone must be unlocked and in close proximity to the Siri

Remote paired to that AppleTV.

After the encrypted connection is made using BLE link encryption, the credential is sent to

AppleTV and is automatically filled in to the relevant text fields on the app.

127Apple Platform Security

Credential provider extensions

In iOS, iPadOS and macOS, users can designate a participating third-party app as a

credential provider for Password AutoFill in Passwords settings (iOS and iPadOS) or in

Extensions settings in System Preferences (macOS). This mechanism is built on app

extensions. The credential provider extension must provide a view for choosing credentials,

and the extension can optionally provide metadata about saved credentials so they can be

offered directly on the QuickType bar (iOS and iPadOS) or in an autocomplete suggestion

(macOS). The metadata includes the website of the credential and the associated

username but not its password. iOS, iPadOS and macOS communicate with the extension

to get the password when the user chooses to fill a credential into an app or a website in

Safari. Credential metadata is stored inside the credential provider app’s container and is

automatically removed when an app is uninstalled.

iCloud Keychain

iCloud Keychain security overview

iCloud allows users to securely sync their passwords between iOS and iPadOS devices and

Mac computers without exposing that information to Apple. In addition to strong privacy

and security, other goals that heavily influenced the design and architecture of iCloud

Keychain were ease of use and the ability to recover a keychain. iCloud Keychain consists

of two services: keychain syncing and keychain recovery.

Apple designed iCloud Keychain and keychain recovery so that a user’s passwords are still

protected under the following conditions:

• A user’s iCloud account is compromised.

• iCloud is compromised by an external attacker or employee.

• A third party accesses user accounts.

Password manager integration with iCloud Keychain

iOS, iPadOS and macOS can automatically generate cryptographically strong random

strings to use as account passwords in Safari. iOS and iPadOS can also generate strong

passwords for apps. Generated passwords are stored in the keychain and synced to other

devices. Keychain items are transferred from device to device, travelling through Apple

servers, but are encrypted in such a way that Apple and other devices can’t read their

contents.

Secure keychain syncing

When a user enables iCloud Keychain for the first time, the device establishes a circle of

trust and creates a syncing identity for itself. The syncing identity consists of a private

key and a public key, and is stored in the device’s keychain. The public key of the syncing

identity is put in the circle, and the circle is signed twice: first by the private key of the

syncing identity, and then again with an asymmetric elliptical key (using P-256) derived

from the user’s iCloud account password. Also stored with the circle are the parameters

(random salt and iterations) used to create the key that’s based on the user’s iCloud

password.

128Apple Platform Security

For two-factor authentication accounts, an additional similar syncing circle is created and

stored in CloudKit. Device identities in this system consist of two pairs of asymmetric

elliptical keys (using P-384), also stored in the keychain. Each device maintains its own list

of identities it trusts, and signs this list using one of its identity keys.

iCloud storage of the syncing circle

The signed syncing circle is stored in the user’s iCloud key-value storage area. It can’t

be read without knowing the user’s iCloud password and is unable to be validly modified

without having the private key of the syncing identity of its member.

For two-factor authentication accounts, each device’s syncing list is stored in CloudKit.

The lists can’t be read without knowing the user’s iCloud password, and they can’t be

modified without having the private keys of the owning device.

How a user’s other devices are added to the syncing circle

When new devices sign in to iCloud, they join the iCloud Keychain syncing circle in one

of two ways: either by pairing with and being sponsored by an existing iCloud Keychain

device, or by using iCloud Keychain recovery.

During the pairing flows, the applicant device creates new syncing identities for both the

syncing circle and the syncing lists (for two-factor authentication accounts) and presents

them to the sponsor. The sponsor adds the public key of the new member to the syncing

circle and signs it again with both its syncing identity and the key derived from the user’s

iCloud password. The new syncing circle is placed in iCloud, where it’s similarly signed by

the new member of the circle. In two-factor authentication accounts, the sponsor device

also provides the joining device with a voucher signed by its identity keys, showing that

the applicant device should be trusted. It then updates its individual list of trusted syncing

identities to include the applicant.

There are now two members of the signing circle and each member has the public key of

its peer. They now begin to exchange individual keychain items through iCloud key-value

storage, or they store them in CloudKit, whichever is most appropriate for the situation. If

both circle members have updates to the same item, one or the other is chosen, resulting

in eventual consistency. Each item that’s synced is encrypted so it can be decrypted only

by a device within the user’s circle of trust; it can’t be decrypted by any other devices or

by Apple.

As new devices join the syncing circle, this “join process” is repeated. For example, when

a third device joins, it can be paired with either of the existing devices. As new peers are

added, each peer syncs with the new one. This is designed to ensure that all members

have the same keychain items.

Only certain items are synced

Some keychain items are device specific, such as iMessage keys, and so must stay

on the device. As a result, every item that will sync must be explicitly marked with the

kSecAttrSynchronizable attribute.

Apple sets this attribute for Safari user data (including usernames, passwords and credit

card numbers) as well as for Wi-Fi passwords, HomeKit encryption keys, and other

keychain items supporting end-to-end iCloud encryption.

Additionally, by default, keychain items added by third-party apps don’t sync. Developers

must set the kSecAttrSynchronizable attribute when adding items to the keychain.

129Apple Platform Security

Secure iCloud Keychain recovery

iCloud Keychain escrows users’ keychain data with Apple without allowing Apple to

read the passwords and other data it contains. Even if the user has only a single device,

keychain recovery provides a safety net against data loss. This is particularly important

when Safari is used to generate random, strong passwords for web accounts because the

only record of those passwords is in the keychain.

A cornerstone of keychain recovery is secondary authentication and a secure escrow

service, created by Apple specifically to support this feature. The user’s keychain is

encrypted using a strong passcode and the escrow service provides a copy of the keychain

only if a strict set of conditions are met.

Use of secondary authentication

There are several ways to establish a strong passcode:

• If two-factor authentication is enabled for the user’s account, the device’s passcode is

used to recover an escrowed keychain.

• If two-factor authentication isn’t set up, the user is asked to create an iCloud security

code by providing a six-digit passcode. Alternatively, without two-factor authentication,

users can specify their own, longer code or they can let their devices create a

cryptographically random code that they can record and keep on their own.

Keychain escrow process

After the passcode is established, the keychain is escrowed with Apple. The iOS, iPadOS

or macOS device first exports a copy of the user’s keychain and then encrypts it wrapped

with keys in an asymmetric keybag and places it in the user’s iCloud key-value storage

area. The keybag is wrapped with the user’s iCloud security code and with the public

key of the hardware security module (HSM) cluster that stores the escrow record. This

becomes the user’s iCloud escrow record. For two-factor authentication accounts, the

keychain is also stored in CloudKit and wrapped to intermediate keys that are recoverable

only with the contents of the iCloud escrow record, thereby providing the same level of

protection.

The contents of the escrow record also allow the recovering device to rejoin iCloud

Keychain, proving to any existing devices that the recovering device successfully

performed the escrow process and so is authorised by the account’s owner.

Note: If the user decides to accept a cryptographically random security code instead of

specifying their own or using a four-digit value, no escrow record is necessary. Instead, the

iCloud security code is used to wrap the random key directly.

Besides establishing a security code, users must register a phone number. This provides

a secondary level of authentication during keychain recovery. The user receives an SMS

message that must be replied to for the recovery to proceed.

130Apple Platform Security

Escrow security for iCloud Keychain

iCloud provides a secure infrastructure for keychain escrow to help ensure that only

authorised users and devices can perform a recovery. Topographically positioned behind

iCloud are clusters of hardware security modules (HSMs) that guard the escrow records.

As described previously, each has a key that is used to encrypt the escrow records under

their watch.

To recover a keychain, users must authenticate with their iCloud account and password and

respond to an SMS sent to their registered phone number. After this is done, users must

enter their iCloud security code. The HSM cluster verifies that a user knows their iCloud

security code using the Secure Remote Password (SRP) protocol; the code itself isn’t sent

to Apple. Each member of the cluster independently verifies that the user hasn’t exceeded

the maximum number of attempts allowed to retrieve their record, as discussed below. If a

majority agree, the cluster unwraps the escrow record and sends it to the user’s device.

Next, the device uses the iCloud security code to unwrap the random keys used to encrypt

the user’s keychain. With that key, the keychain — retrieved from iCloud key-value storage

and CloudKit — is decrypted and restored onto the device. iOS, iPadOS and macOS

allow only 10 attempts to authenticate and retrieve an escrow record. After several failed

attempts, the record is locked and the user must call Apple Support to be granted more

attempts. After the 10th failed attempt, the HSM cluster destroys the escrow record and

the keychain is lost forever. This provides protection against a brute-force attempt to

retrieve the record, at the expense of sacrificing the keychain data in response.

These policies are coded in the HSM firmware. The administrative access cards that permit

the firmware to be changed have been destroyed. Any attempt to alter the firmware or

access the private key causes the HSM cluster to delete the private key. Should this occur,

the owner of each keychain protected by the cluster receives a message informing them

that their escrow record has been lost. They can then choose to re-enrol.

ApplePay

ApplePay security overview

With ApplePay, users can use supported iPhone, iPad, Mac and AppleWatch devices to

pay in an easy, secure and private way in shops, apps and on the web in Safari. Users can

also add ApplePay–enabled travel, student ID and access cards to Apple Wallet. It’s simple

for users and it’s built with integrated security in both hardware and software.

ApplePay is also designed to protect the user’s personal information. ApplePay doesn’t

collect any transaction information that can be tied back to the user. Payment transactions

are between the user, the merchant and the card issuer.

ApplePay component security

ApplePay uses several hardware and software features to provide secure, reliable

purchases.

131Apple Platform Security

Secure Element

The Secure Element is an industry-standard certified chip running the Java Card platform,

which is compliant with financial industry requirements for electronic payments. The

Secure Element IC and the Java Card platform are certified in accordance with the EMVCo

Security Evaluation process. After the successful completion of the security evaluation,

EMVCo issues unique IC and platform certificates.

The Secure Element IC has been certified based on the Common Criteria standard. For

more information, see Secure Enclave Processor security certifications in Apple Platform

Certifications.

NFC controller

The NFC controller handles Near Field Communication protocols and routes communication

between the Application Processor and the Secure Element, and between the Secure

Element and the point-of-sale terminal.

Apple Wallet

The Apple Wallet app is used to add and manage credit, debit and store cards, and to make

payments with ApplePay. Users can view their cards and may be able to view additional

information provided by their card issuer, such as their card issuer’s privacy policy, recent

transactions and more in Apple Wallet. Users can also add cards to ApplePay in:

• Setup Assistant and Settings for iOS and iPadOS

• The Watch app for AppleWatch

• Wallet & ApplePay in System Preferences for Mac computers with TouchID

In addition, Apple Wallet allows users to add and manage travel cards, rewards cards,

boarding passes, tickets, gift cards, student ID cards, access cards and more.

Secure Enclave

On iPhone, iPad, AppleWatch, Mac computers with TouchID, and Mac computers with

Apple silicon that use the Magic Keyboard with TouchID, the Secure Enclave manages the

authentication process and allows a payment transaction to proceed.

On AppleWatch, the device must be unlocked and the user must double-click the side

button. The double-click is detected and passed directly to the Secure Element or Secure

Enclave, where available, without going through the Application Processor.

ApplePay servers

The ApplePay servers manage the setup and provisioning of credit, debit, travel, student

ID and access cards in Apple Wallet. The servers also manage the Device Account

Numbers stored in the Secure Element. They communicate both with the device and with

the payment network or card issuer servers. The ApplePay servers are also responsible for

re-encrypting payment credentials for payments within apps or on the web.

132Apple Platform Security

How ApplePay keeps users’ purchases protected

Secure Element

The Secure Element hosts a specially designed applet to manage ApplePay. It also

includes applets certified by payment networks or card issuers. Credit, debit or pre-paid

card data is sent from the payment network or card issuer encrypted to these applets using

keys that are known only to the payment network or card issuer and the applets’ security

domain. This data is stored within these applets and protected using the Secure Element’s

security features. During a transaction, the terminal communicates directly with the

Secure Element through the Near Field Communication (NFC) controller over a dedicated

hardware bus.

NFC controller

As the gateway to the Secure Element, the NFC controller helps ensure that all contactless

payment transactions are conducted using a point-of-sale terminal that’s in close proximity

to the device. Only payment requests arriving from an in-field terminal are marked by the

NFC controller as contactless transactions.

After a credit, debit or pre-paid card (including store cards) payment is authorised by

the cardholder using FaceID, TouchID or a passcode, or on an unlocked AppleWatch

by double-clicking the side button, contactless responses prepared by the payment

applets within the Secure Element are exclusively routed by the controller to the NFC

field. Consequently, payment authorisation details for contactless payment transactions

are contained to the local NFC field and are never exposed to the Application Processor.

In contrast, payment authorisation details for payments within apps and on the web are

routed to the Application Processor, but only after encryption by the Secure Element to the

ApplePay server.

Credit, debit and pre-paid cards

Card provisioning security overview

When a user adds a credit, debit or pre-paid card (including store cards) to Apple Wallet,

Apple securely sends the card information, along with other information about user’s

account and device, to the card issuer or card issuer’s authorised service provider.

Using this information, the card issuer determines whether to approve adding the card to

Apple Wallet. As part of the card provisioning process, ApplePay uses three server-side

calls to send and receive communication with the card issuer or network:

• Required Fields

• Check Card

• Link and Provision

The card issuer or network uses these calls to verify, approve and add cards to

Apple Wallet. These client-server sessions use TLS 1.2 to transfer the data.

133Apple Platform Security

Full card numbers aren’t stored on the device or on ApplePay servers. Instead, a unique

Device Account Number is created, encrypted and then stored in the Secure Element. This

unique Device Account Number is encrypted in such a way that Apple can’t access it. The

Device Account Number is unique and different from most credit or debit card numbers;

the card issuer or payment network can prevent its use on a magnetic stripe card, over

the phone or on websites. The Device Account Number in the Secure Element is never

stored on ApplePay servers or backed up to iCloud, and it is isolated from iOS, iPadOS and

watchOS devices, and from Mac computers with TouchID.

Cards for use with AppleWatch are provisioned for ApplePay using the AppleWatch app

on iPhone or within a card issuer’s iPhone app. Adding a card to AppleWatch requires that

the watch be within Bluetooth communications range. Cards are specifically enrolled for

use with AppleWatch and have their own Device Account Numbers which are stored within

the Secure Element on the AppleWatch.

When credit, debit or pre-paid cards (including store cards) are added, they appear on

a list of cards during Setup Assistant on devices that are signed in to the same iCloud

account. These cards remain on this list for as long as they are active on at least one

device. Cards are removed from this list after they have been removed from all devices for

7 days. This feature requires two-factor authentication to be enabled on the respective

iCloud account.

Adding credit or debit cards to ApplePay

Credit cards can be manually added to ApplePay in Apple devices.

Adding credit or debit cards manually

To add a card manually, the name, card number, expiry date and CVV are used to facilitate

the provisioning process. From within Settings, Apple Wallet or the AppleWatch app, users

can enter that information either by typing or by using the device’s camera. When the

camera captures the card information, Apple attempts to populate the name, card number

and expiry date. The photo is never saved to the device or stored in the photo library. After

all the fields are filled in, the Check Card process verifies the fields other than the CVV.

They are then encrypted and sent to the ApplePay server.

If a terms and conditions ID is returned with the Check Card process, Apple downloads

and displays the terms and conditions of the card issuer to the user. If the user accepts

the terms and conditions, Apple sends the ID of the terms that were accepted as well as

the CVV to the Link and Provision process. Additionally, as part of the Link and Provision

process, Apple shares information from the device with the card issuer or network. This

includes information about (a) the user’s iTunes and AppStore account activity (for

example, whether the user has a long history of transactions within iTunes), (b) the user’s

device (for example, the phone number, name and model of the user’s device plus any

companion Apple device necessary to set up ApplePay), and (c) the user’s approximate

location at the time the user adds their card (if the user has Location Services enabled).

Using this information, the card issuer determines whether to approve adding the card to

ApplePay.

134Apple Platform Security

As the result of the Link and Provision process, two things occur:

• The device begins to download the Apple Wallet pass file representing the credit or

debit card.

• The device begins to bind the card to the Secure Element.

The pass file contains URLs to download card art, metadata about the card such as contact

information, the related issuer’s app and supported features. It also contains the pass

state, which includes information such as whether the personalising of the Secure Element

has completed, whether the card is currently suspended by the card issuer or whether

additional verification is required before the card can make payments with ApplePay.

Adding credit or debit cards from an iTunesStore account

For a credit or debit card on file with iTunes, the user may be required to re-enter their

AppleID password. The card number is retrieved from iTunes and the Check Card process

is initiated. If the card is eligible for ApplePay, the device downloads and displays terms

and conditions, then sends along the terms’ ID and the card security code to the Link and

Provision process. Additional verification may occur for iTunes account cards on file.

Adding credit or debit cards from a card issuer’s app

When an app is registered for use with ApplePay, keys are established for the app and for

the card issuer’s server. These keys are used to encrypt the card information that’s sent to

the card issuer. This is designed to prevent the information from being read by the Apple

device. The provisioning flow is similar to that used for manually added cards, described

previously, except single-use passwords are used in lieu of the CVV.

Adding credit or debit cards from a card issuer’s website

Some card issuers provide the ability to initiate the card provisioning process for

Apple Wallet directly from their websites. In this case, the user initiates the task by

selecting a card to provision on the card issuer’s website. The user is then directed to a

self-contained Apple sign-in experience (contained within Apple’s domain) and is asked to

devices to provision the card to and is required to confirm the provisioning result on each

respective target device.

Adding additional verification

A card issuer can decide whether a credit or debit card requires additional verification.

Depending on what’s offered by the card issuer, the user may be able to choose between

different options for additional verification, such as a text message, email, customer

service call or a method in an approved third-party app to complete the verification. For

text messages or email, the user selects from contact information the issuer has on file.

A code is sent, which must be entered into Apple Wallet, Settings or the AppleWatch

app. For customer service or verification using an app, the issuer performs their own

communication process.

135Apple Platform Security

Payment authorisation with ApplePay

For devices having a Secure Enclave, a payment can be made only after it receives

authorisation from the Secure Enclave. On iPhone or iPad, this involves confirming that the

user has authenticated with FaceID, TouchID or the device passcode. FaceID or TouchID,

if available, is the default method, but the passcode can be used at any time. A passcode

is automatically offered after three unsuccessful attempts to match a fingerprint or two

unsuccessful attempts to match a face; after five unsuccessful attempts, the passcode is

required. A passcode is also required when FaceID or TouchID isn’t configured or isn’t

enabled for ApplePay. For a payment to be made on AppleWatch, the device must be

unlocked with passcode and the side button must be double-clicked.

Using a shared pairing key

Communication between the Secure Enclave and the Secure Element takes place over a

serial interface, with the Secure Element connected to the NFC controller, which in turn

is connected to the Application Processor. Though not directly connected, the Secure

Enclave and Secure Element can communicate securely using a shared pairing key that’s

provisioned during the manufacturing process. The encryption and authentication of the

communication are based on AES, with cryptographic nonces used by both sides to protect

against replay attacks. The pairing key is generated inside the Secure Enclave from its UID

key and the Secure Element unique identifier. The pairing key is then securely transferred

from the Secure Enclave to a hardware security module (HSM) in the factory, which has the

key material required to then inject the pairing key into the Secure Element.

Authorising a secure transaction

When the user authorises a transaction, which includes a physical gesture communicated

directly to the Secure Enclave, the Secure Enclave then sends signed data about the

type of authentication and details about the type of transaction (contactless or within

apps) to the Secure Element, tied to an Authorization Random (AR) value. The AR value

is generated in the Secure Enclave when a user first provisions a credit card and persists

while ApplePay is enabled, protected by the Secure Enclave encryption and anti-rollback

mechanism. It’s securely delivered to the Secure Element by leveraging the pairing key.

On receipt of a new AR value, the Secure Element marks any previously added cards as

deleted.

Using a payment cryptogram for dynamic security

Payment transactions originating from the payment applets include a payment cryptogram

along with a Device Account Number. This cryptogram, a single-use code, is computed

using a transaction counter and a key. The transaction counter is incremented for each

new transaction. The key is provisioned in the payment applet during personalisation and

is known by the payment network or the card issuer, or both. Depending on the payment

scheme, other data may also be used in the calculation, including:

• A Terminal Unpredictable Number, for Near Field Communication (NFC) transactions

• An ApplePay server nonce, for transactions within apps

These security codes are provided to the payment network and to the card issuer, which

allows the issuer to verify each transaction. The length of these security codes may vary

based on the type of transaction.

136Apple Platform Security

Paying with cards using ApplePay

ApplePay can be used to pay for purchases in shops, within apps and on websites.

Paying with cards in stores

If iPhone or AppleWatch is on and detects an NFC field, it presents the user with the

requested card (if automatic selection is turned on for that card) or the default card, which

is managed in Settings. The user can also go to Apple Wallet and choose a card, or when

the device is locked, can:

• Double-click the side button on devices with FaceID

• Double-click the Home button on devices with TouchID

• Use Accessibility features that allow ApplePay from the Lock Screen

Next, before information is transmitted, the user must authenticate using FaceID, TouchID

or their passcode. When AppleWatch is unlocked, double-clicking the side button

activates the default card for payment. No payment information is sent without user

authentication.

After the user authenticates, the Device Account Number and a transaction-specific

dynamic security code are used when processing the payment. Neither Apple nor a user’s

device sends the full credit or debit card numbers to merchants. Apple may receive

anonymous transaction information such as the approximate time and location of the

transaction, which helps improve ApplePay and other Apple products and services.

Paying with cards within apps

ApplePay can also be used to make payments on iPhone, iPad, Mac and AppleWatch apps.

When users pay within apps using ApplePay, Apple receives the encrypted transaction

information. Before that information is sent to the developer or merchant, Apple re-

encrypts the transaction with a developer-specific key. ApplePay retains anonymous

transaction information such as approximate purchase amount. This information can’t be

tied to the user and never includes what the user is buying.

When an app initiates an ApplePay payment transaction, the ApplePay servers receive the

encrypted transaction from the device prior to the merchant receiving it. The ApplePay

servers then re-encrypt the transaction with a merchant-specific key before relaying it to

the merchant.

When an app requests a payment, it calls an API to determine whether the device supports

ApplePay and whether the user has credit or debit cards that can make payments on a

payment network accepted by the merchant. The app requests any pieces of information

it needs to process and fulfil the transaction, such as the billing and shipping address, and

contact information. The app then asks iOS, iPadOS or watchOS to present the ApplePay

sheet, which requests information for the app as well as other necessary information, such

as the card to use.

At this time, the app is presented with town/city, county and postcode information to

calculate the final shipping cost. The full set of requested information isn’t provided to the

app until the user authorises the payment with FaceID, TouchID or the device passcode.

After the payment is authorised, the information presented in the ApplePay sheet is

transferred to the merchant.

137Apple Platform Security

App payment authorisation

When the user authorises the payment, a call is made to the ApplePay servers to obtain

a cryptographic nonce, which is similar to the value returned by the NFC terminal used

for in-store transactions. The nonce, along with other transaction data, is passed to the

Secure Element to compute a payment credential that’s encrypted with an Apple key.

The encrypted payment credential is returned to the ApplePay servers, which decrypt

the credential, verify the nonce in the credential against the nonce originally sent by

the ApplePay servers, and re-encrypt the payment credential with the merchant key

associated with the Merchant ID. The payment is then returned to the device, which hands

it back to the app through the API. The app then passes it along to the merchant system for

processing. The merchant can then decrypt the payment credential with its private key for

processing. This, together with the signature from Apple’s servers, allows the merchant to

verify that the transaction was intended for this particular merchant.

The APIs require an entitlement that specifies the supported Merchant IDs. An app can

also include additional data (such as an order number or customer identity) to send to the

Secure Element to be signed, ensuring that the transaction can’t be diverted to a different

customer. This is accomplished by the app developer, who can specify applicationData on

the PKPaymentRequest. A hash of this data is included in the encrypted payment data. The

merchant is then responsible for verifying that their applicationData hash matches what’s

included in the payment data.

Paying with cards at websites

ApplePay can be used to make payments at websites on iPhone, iPad, AppleWatch

and Mac computers with TouchID. ApplePay transactions can also start on a Mac and

be completed on an ApplePay–enabled iPhone or AppleWatch using the same iCloud

account.

ApplePay on the web requires that all participating websites register with Apple. After

the domain is registered, domain name validation is performed only after Apple issues a

TLS client certificate. Websites supporting ApplePay are required to serve their content

over HTTPS. For each payment transaction, websites need to obtain a secure and unique

merchant session with an Apple server using the Apple-issued TLS client certificate.

Merchant session data is signed by Apple. After a merchant session signature is verified,

a website may query whether the user has an ApplePay–capable device and whether they

have a credit, debit or pre-paid card activated on the device. No other details are shared.

If the user doesn’t want to share this information, they can disable ApplePay queries in

Safari privacy settings on iPhone, iPad and Mac devices.

After a merchant session is validated, all privacy and security measures are the same as

when a user pays within an app.

138Apple Platform Security

If the user is transmitting payment-related information from a Mac to an iPhone or

AppleWatch, ApplePay Handoff uses the end-to-end encrypted AppleIDentity Service

(IDS) protocol to transmit payment-related information between the user’s Mac and

the authorising device. The IDS client on Mac uses the user’s device keys to perform

encryption so no other device can decrypt this information, and the keys aren’t available to

Apple. Device discovery for ApplePay Handoff contains the type and unique identifier of

the user’s credit cards along with some metadata. The device-specific account number of

the user’s card isn’t shared and it continues to remain stored securely on the user’s iPhone

or AppleWatch. Apple also securely transfers the user’s recently used contact, shipping

and billing addresses over iCloud Keychain.

After the user authorises payment using FaceID, TouchID, a passcode, or by double-

clicking the side button on AppleWatch, a payment token uniquely encrypted to

each website’s merchant certificate is securely transmitted from the user’s iPhone or

AppleWatch to their Mac, and then delivered to the merchant’s website.

Only devices in proximity to each other may request and complete payment. Proximity is

determined through Bluetooth Low Energy (BLE) advertisements.

Contactless passes in ApplePay

To transmit data from supported passes to compatible NFC terminals, Apple uses the

Apple Value Added Services (Apple VAS) protocol. The VAS protocol can be implemented

on contactless terminals or in iPhone apps and uses NFC to communicate with supported

Apple devices. The VAS protocol works over a short distance and can be used to present

contactless passes independently or as part of an ApplePay transaction.

When the device is held near the NFC terminal, the terminal initiates receiving the pass

information by sending a request for a pass. If the user has a pass with the pass provider’s

identifier, the user is asked to authorise its use using FaceID, TouchID or a passcode. The

pass information, a timestamp and a single-use random ECDH P-256 key are used with the

pass provider’s public key to derive an encryption key for the pass data, which is sent to

the terminal.

From iOS 12.0.1 up to and including iOS 13, users may manually select a pass before

presenting it to the merchant’s NFC terminal. In iOS 13.1 or later, pass providers can

configure manually selected passes to either require user authentication or be used

without authentication.

139Apple Platform Security

Rendering cards unusable with ApplePay

Credit, debit and prepaid cards added to the Secure Element can be used only if

the Secure Element is presented with authorisation using the same pairing key and

Authorisation Random (AR) value from when the card was added. On receipt of a new AR

value, the Secure Element marks any previously added cards as deleted. This allows the

operating system to instruct the Secure Enclave to render cards unusable by marking its

copy of the AR as invalid under the following scenarios:

Method Device

The passcode is disabled. i Phone, i Pad, AppleWatch

The password is disabled. Mac

The user signs out of i Cloud. i Phone, i Pad, Mac, AppleWatch

The user selects Erase All Content and Settings. i Phone, i Pad, Mac, AppleWatch

The device is restored from Recovery Mode. i Phone, i Pad, Mac, AppleWatch

Unpairing AppleWatch

Suspending, removing and erasing cards

Users can suspend ApplePay on iPhone, iPad and AppleWatch by placing their devices

in Lost Mode using Find My. Users also have the ability to remove and erase their cards

from ApplePay using Find My, iCloud.com, or directly on their devices using Apple Wallet.

On AppleWatch, cards can be removed using iCloud settings, the AppleWatch app on

iPhone or directly on the watch. The ability to make payments using cards on the device is

suspended or removed from ApplePay by the card issuer or respective payment network

even if the device is offline and not connected to a mobile or Wi-Fi network. Users can also

call their card issuer to suspend or remove cards from ApplePay.

When a user erases the entire device — using Erase All Content and Settings, using

Find My or restoring their device — iPhone, iPad, iPodtouch, Mac and AppleWatch instruct

the Secure Element to mark all cards as deleted. This has the effect of immediately

changing the cards to an unusable state until the ApplePay servers can be contacted to

fully erase the cards from the Secure Element. Independently, the Secure Enclave marks

the AR as invalid so that further payment authorisations for previously enrolled cards aren’t

possible. When the device is online, it attempts to contact the ApplePay servers to help

ensure that all cards in the Secure Element are erased.

140Apple Platform Security

Apple Card security

On supported models of iPhone and Mac, a user can securely apply for an Apple Card.

Apple Card application

In iOS 12.4 or later, macOS 10.14.6 or later and watchOS 5.3 or later, Apple Card can be

used with ApplePay to make payments in stores, in apps and on the web.

To apply for Apple Card, the user must be signed in to their iCloud account on an

ApplePay–compatible iOS or iPadOS device and have two-factor authentication set

up on the iCloud account. When the application is approved, Apple Card is available in

Apple Wallet or within Settings > Wallet & ApplePay across any of the eligible devices the

user has signed in with their AppleID.

When a user applies for Apple Card, user identity information is securely verified by Apple’s

identity provider partners and then shared with Goldman Sachs Bank USA for the purposes

of identity and credit evaluation.

Information such as the social security number or ID document image provided during the

application is securely transmitted to Apple’s identity provider partners and/or Goldman

Sachs Bank USA encrypted with their respective keys. Apple can’t decrypt this data.

The income information provided during the application and the bank account information

used for bill payments are securely transmitted to Goldman Sachs Bank USA encrypted

with their key. The bank account information is saved in the keychain. Apple can’t decrypt

this data.

When adding Apple Card to Apple Wallet, the same information as when a user adds a

credit or debit card may be shared with Apple’s partner bank Goldman Sachs Bank USA,

and with ApplePayments Inc. This information is used only for troubleshooting, fraud

prevention and regulatory purposes.

In iOS 14.6 or later, iPadOS 14.6 or later, and watchOS 7.5 or later, the organiser of an

iCloud family with an Apple Card can share their card with their iCloud Family members

over the age of 13. User authentication is required to confirm the invitation. Apple Wallet

uses a key in the Secure Enclave to compute a signature that binds the owner and the

invitee. That signature is validated on Apple servers.

Optionally, the organiser can set a transaction limit for the participants. Participant cards

can also be locked to pause their spending at any time through Apple Wallet. When a

co-owner or participant over the age of 18 accepts the invitation and applies, they go

through the same application process as defined in the Apple Card application section in

Apple Wallet.

Apple Card usage

A physical card can be ordered from Apple Card in Apple Wallet. After the user receives

the physical card, it’s activated using the NFC tag that’s in the bifold envelope of the

physical card. The tag is unique per card and can’t be used to activate another user’s card.

Alternatively, the card can be manually activated in Apple Wallet settings. Additionally, the

user can also choose to lock or unlock the physical card at any time from Apple Wallet.

141Apple Platform Security

Apple Card payments and Apple Wallet pass details

Payments due on the Apple Card account can be made from Apple Wallet in iOS with

Apple Cash and a bank account. Bill payments can be scheduled as recurring or as a

one-off payment at a specific date with Apple Cash and a bank account. When a user

makes a payment, a call is made to the ApplePay servers to obtain a cryptographic nonce

similar to Apple Cash. The nonce, along with the payment setup details, is passed to the

Secure Element to compute a signature. The signature is then returned to the ApplePay

servers. The authentication, integrity and correctness of the payment are verified through

the signature and the nonce by ApplePay servers and the order is passed on to Goldman

Sachs Bank USA for processing.

The Apple Card number is retrieved by Apple Wallet by presenting a certificate. The

ApplePay Server validates the certificate to confirm the key was generated in the Secure

Enclave. It then uses this key to encrypt the Apple Card number before returning it to

Apple Wallet, so that only the iPhone that requested the Apple Card number can decrypt it.

After decryption, the Apple Card number is saved in iCloud Keychain.

Displaying the Apple Card number details in the pass using Apple Wallet requires user

authentication with FaceID, TouchID or a passcode. It can be replaced by the user in the

card information section, which disables the previous one.

Advanced Fraud Protection

In iOS15 or later and iPadOS15 or later, the Apple Card user can enable Advanced

Fraud Protection in Apple Wallet. When enabled, the Card Security Code refreshes every

few days.

Apple Cash security

In iOS 11.2 or later, iPadOS 13.1 or later, and watchOS 4.2 or later, ApplePay can be used

on an iPhone, iPad or AppleWatch to send, receive and request money from other users.

When a user receives money, it’s added to an Apple Cash account that can be accessed in

Apple Wallet or within Settings > Wallet & ApplePay across any of the eligible devices the

user has signed in with their AppleID.

In iOS 14, iPadOS14 and watchOS 7, the organiser of an iCloud family who has verified

their identity with Apple Cash can enable Apple Cash for their family members under the

age of 18. Optionally, the organiser can restrict the money sending capabilities of these

users to family members only or contacts only. If the family member under the age of 18

goes through an AppleID account recovery, the organiser of the family must manually re-

enable the Apple Cash card for that user. If the family member under the age of 18 is no

longer part of the iCloud family, their Apple Cash balance is automatically transferred to

the organiser’s account.

When the user sets up Apple Cash, the same information as when the user adds a credit or

debit card may be shared with our partner bank Green Dot Bank and with ApplePayments

Inc., a wholly owned subsidiary created to protect the user’s privacy by storing and

processing information separately from the rest of Apple and in a way that the rest of

Apple doesn’t know. This information is used only for troubleshooting, fraud prevention and

regulatory purposes.

142Apple Platform Security

Using Apple Cash in iMessage

To use person-to-person payments and Apple Cash, a user must be signed in to their

iCloud account on an Apple Cash–compatible device and have two-factor authentication

set up on the iCloud account. Money requests and transfers between users are initiated

from within the Messages app or by asking Siri. When a user attempts to send money,

iMessage displays the ApplePay sheet. The Apple Cash balance is always used first. If

necessary, additional funds are drawn from a second credit or debit card the user has

added to Apple Wallet.

Using Apple Cash in shops, apps and on the web

The Apple Cash card in Apple Wallet can be used with ApplePay to make payments in

shops, in apps and on the web. Money in the Apple Cash account can also be transferred

to a bank account. In addition to money being received from another user, money can be

added to the Apple Cash account from a debit or pre-paid card in Apple Wallet.

ApplePayments Inc. stores and may use, the user’s transaction data for troubleshooting,

fraud prevention and regulatory purposes once a transaction is completed. The rest of

Apple doesn’t know who the user sent money to, received money from or where the user

made a purchase with their Apple Cash card.

When the user sends money with ApplePay, adds money to an Apple Cash account or

transfers money to a bank account, a call is made to the ApplePay servers to obtain a

cryptographic nonce, which is similar to the value returned for ApplePay within apps. The

nonce, along with other transaction data, is passed to the Secure Element to compute a

payment signature. The signature is returned to the ApplePay servers. The authentication,

integrity and correctness of the transaction is verified through the payment signature and

the nonce by ApplePay servers. Money transfer is then initiated and the user is notified of

a completed transaction.

If the transaction involves:

• A debit card for adding money to Apple Cash

• Providing supplemental money if the Apple Cash balance is insufficient

An encrypted payment credential is also produced and sent to ApplePay servers, similar to

how ApplePay works within apps and websites.

After the balance of the Apple Cash account exceeds a certain amount or if unusual activity

is detected, the user is prompted to verify their identity. Information provided to verify the

user’s identity — such as social security number or answers to questions (for example, to

confirm a street name the user lived on previously) — is securely transmitted to the Apple

partner and encrypted using their key. Apple can’t decrypt this data. The user is prompted

to verify their identity again if they perform an AppleID account recovery, before regaining

access to their Apple Cash balance.

143Apple Platform Security

Tap to Pay on iPhone security

Tap to Pay on iPhone, available in iOS 15.4, allows US merchants to accept ApplePay and

other contactless payments by using iPhone and a partner-enabled iOS app. With this

service, users with supported iPhone devices can securely accept contactless payments

and ApplePay NFC-enabled passes. With Tap to Pay on iPhone, merchants don’t need

additional hardware to accept contactless payments.

Tap to Pay on iPhone is designed to protect the payer’s personal information. This service

doesn’t collect transaction information that can be tied back to the payer. Payment card

information such as Credit/Debit Card Number (PAN) is secured by the Secure Element

and isn’t available to the merchant. The payment card information stays between the

merchant’s Payment Service Provider, the payer and the card issuer. In addition, the Tap to

Pay service doesn’t collect payer’s names, addresses or phone numbers.

Tap to Pay on iPhone has been assessed externally by an accredited security laboratory

and approved by American Express, Discover, Mastercard and Visa.

Contactless payment component security

• Secure Element: The Secure Element [Link to ApplePay Secure Element section] hosts

the payment kernels, which read and secure the contactless payment card data.

• NFC Controller: The NFC controller handles Near Field Communication protocols and

routes communication between the Application Processor and the Secure Element, and

between the Secure Element and the contactless payment card.

• Tap to Pay on iPhone servers: The Tap to Pay on iPhone servers manage the setup and

provisioning of the payment kernels in the device. The servers also monitor the security

of the Tap to Pay on iPhone devices in a manner compatible with the Contactless

Payments on COTS (CPoC) standard from the Payment Card Industry Security

Standards Council (PCI SSC), and are PCI DSS compliant.

How Tap to Pay reads credit, debit and pre-paid cards

Provisioning security overview

Upon first use of Tap to Pay on iPhone using a sufficiently entitled app, the Tap to Pay

on iPhone server determines whether the device meets the eligibility criteria such as

Device Model, iOS version and whether a passcode has been set. After this verification

is complete, the payment acceptance applet is downloaded from the Tap to Pay on

iPhone server and installed on the Secure Element, along with the associated payment

kernel configuration. This operation is performed securely between the Tap to Pay on

iPhone servers and the Secure Element. The Secure Element validates the integrity and

authenticity of this data prior to installation.

Card read security overview

When a Tap to Pay on iPhone app requests a card read from ProximityReader framework, a

sheet — controlled by iOS — is displayed and prompts the user to tap a payment card. iOS

initialises the Payment Card Reader and then requests the payment kernels in the Secure

Element to initiate a card read.

144Apple Platform Security

At this point, the Secure Element assumes control of the NFC controller in Reader Mode.

This mode allows only card data to be exchanged between the payment card and the

Secure Element through the NFC controller. Payment cards can be read only while in

this mode.

After the payment acceptance applet on the Secure Element has completed the card read,

it encrypts and signs the card data. The card data remains encrypted and authenticated

until it reaches the Payment Service Provider. Only the Payment Service Provider used by

the app to request the card read can decrypt the card data. The Payment Service Provider

must request the card data decryption key from the Tap to Pay on iPhone server. The

Tap to Pay on iPhone server emits decryption keys to the Payment Service Provider after

validation of the integrity and authenticity of the data, and after verifying that the card read

was within 60 seconds of the card read on the device.

This model helps ensure that the card data can’t be decrypted by anyone other than the

Payment Service Provider, which processes this transaction for the merchant.

Using Apple Wallet

Access using Apple Wallet

In Apple Wallet on supported iPhone and AppleWatch devices, users can store keys to

their homes, cars and hotel rooms. They can even store corporate badges and student

ID cards. When a user arrives at a door, the right key is automatically presented, allowing

them to enter with just a tap using Near Field Communication (NFC).

User convenience

When a key, pass, student ID card or corporate badge is added to Apple Wallet, Express

Mode is turned on by default. Cards in Express Mode interact with accepting terminals

without FaceID, TouchID, passcode authentication, or double-clicking the side button on

AppleWatch. To disable this feature, users can turn off Express Mode by tapping the More

button on the front of the card in Apple Wallet. To turn Express Mode back on, they must

use FaceID, TouchID or a passcode.

Privacy and security

Keys in Apple Wallet take full advantage of the privacy and security built into iPhone and

AppleWatch. When or where a person uses their keys in Apple Wallet is never shared with

Apple or stored on Apple servers, and credentials are securely stored inside the Secure

Element (SE) of supported devices. The SE hosts specially designed applets to securely

manage and store access keys, ensuring that keys can’t be extracted.

Before provisioning any access keys, a user must be signed in to their iCloud account on a

compatible iPhone and have two-factor authentication turned on for their iCloud account,

with the exception of a student ID, which doesn’t require two-factor authentication to be

turned on.

When a user initiates the provisioning process, similar steps to those involved in credit

and debit card provisioning take place, such as link and provisioning. During a transaction,

the reader communicates with the Secure Element through the Near Field Communication

(NFC) controller using an established secure channel.

145Apple Platform Security

The number of devices, including iPhone and AppleWatch, that can be provisioned with

an access key is defined and controlled by each partner and can vary from one partner to

another. Such an approach allows each partner to have control over the maximum number

of provisioned access keys per device type to suit their specific needs. For this purpose,

Apple supplies partners with device type and anonymised device identifiers. Identifiers are

different for every partner for privacy and security reasons.

Keys can be disabled or removed by:

• Erasing the device remotely with Find My

• Enabling Lost Mode with Find My

• Receiving a mobile device management (MDM) remote wipe command

• Removing all cards from their AppleID account page

• Removing all cards from iCloud.com

• Removing all cards from Apple Wallet

• Removing the card in the issuer’s app

In iOS 15.4 or later, when a user double-clicks the side button on an iPhone with FaceID

or double-clicks the Home button on an iPhone with TouchID, their passes and access

key details aren’t displayed until they authenticate to the device. Either FaceID, TouchID

or passcode authentication is required before pass-specific information, including hotel

booking details, are displayed in Apple Wallet.

Access credential types

There are different types of access from Apple Wallet, such as hospitality, corporate

badges, student IDs, home keys and car keys.

Hospitality

Hotel room keys in Apple Wallet help deliver an easy and contactless experience from

check-in to check-out, while providing additional privacy and security benefits for guests

on top of traditional plastic hotel key cards. Hotel guests at supported locations can tap to

unlock with room keys in Apple Wallet on their compatible iPhone devices and AppleWatch

Series 4 or later.

The capabilities in Apple Wallet are specifically designed to reduce friction for the

customer:

• Pre-arrival provisioning from the hotel’s app to add a pass to Apple Wallet ahead of a stay

• Check-in pass tiles to initiate check-ins and room assignments from Apple Wallet

• Post-provisioning key updates to support extending or modifying current stays

• Multi-room key support for a single pass in Apple Wallet

• Auto-archiving of expired keys in Apple Wallet

146Apple Platform Security

Corporate badges

Employee badges of supported partners can be added to Apple Wallet on iPhone and

AppleWatch, allowing employees around the world to have contactless access to their

workplaces. To add a badge, an employee must have multifactor authentication enabled for

their account used to sign in to the app provided by their employer.

Employee badge takes advantage of Apple’s access capabilities, allowing users to:

• Automatically add an employee badge to their paired AppleWatch through push

provisioning that doesn’t require installing a partner’s app

• Seamlessly access office amenities utilising express mode

• Gain access to the workplace even after their iPhone runs out of battery

Student ID cards

In iOS12 or later, students and staff at participating schools and campuses can add their

student ID card to Apple Wallet on supported models of iPhone and AppleWatch to access

locations and pay wherever their card is accepted.

A user adds their student ID card to Apple Wallet through an app provided by the card

issuer or participating institution. The technical process by which this occurs is the same

as the one described in Adding credit or debit cards from a card issuer’s app. In addition,

issuing apps must support two-factor authentication on the accounts that guard access to

their student IDs. A card may be set up simultaneously on up to any two supported Apple

devices signed in with the same AppleID.

Multi-family homes

Tenants and staff of supported partner facilities can use their home key in Apple Wallet to

access their building, unit and common areas. The home key can be provisioned from the

app provided by the partner. For partners that support frictionless provisioning, property

managers can send tenants a link to initiate provisioning using their preferred messaging

channel (for example, email or SMS) so that the tenant only needs to click the link to

redeem the key. App Clips also provide a secure and seamless experience, making it

possible to provision a key without installing a partner’s app. For more information, see the

Apple Support article Use App Clips on iPhone.

Home key

A home key in Apple Wallet can be used with supported NFC-enabled door locks with a simple

tap of an iPhone or AppleWatch. For more information about how a user can set up and use a

home key, see the Apple Support article Unlock your door with a home key on iPhone.

When a user sets up a home key, all residents in their household also automatically receive

the home key. To further share a home key or remove a member of a shared home, the

owner of a home can use the Home app to manage invitations and members. When a user

chooses to accept an invitation to join a home with a home key, this initiates provisioning

of the home key into Apple Wallet on their devices. If a user chooses to leave a home or

if the home owner withdraws their access, these actions also remove the home key from

Apple Wallet.

147Apple Platform Security

Car key

Storing car keys digitally in Apple Wallet is supported natively in compatible iPhone devices

and paired AppleWatch devices. Car keys are represented as passes (created by Apple

on behalf of the carmaker) in Apple Wallet and support the full ApplePay card life cycle

(iCloud Lost Mode, Remote Wipe, local pass deletion, and Erase All Content and Settings).

In addition to the standard ApplePay card management, shared car keys can be deleted

from the owner’s iPhone, AppleWatch, and in the vehicle’s Human Machine Interface (HMI).

Car keys can be used to unlock and lock the vehicle and to start the engine or set the

vehicle into drive mode. The “standard transaction” offers mutual authentication and is

mandatory for engine start. Unlock and lock transactions may use the “fast transaction”

when required for performance reasons.

Keys are created through pairing an iPhone with an owned and supported vehicle. All

keys are created on the embedded Secure Element based on elliptic curve (NIST P-256)

onboard key generation (ECC-OBKG), and the private keys never leave the Secure Element.

Communication between devices and the vehicle use either NFC or a combination of

Bluetooth LE and UWB, and key management uses an Apple-to-carmaker server API with

mutually authenticated TLS. After a key is paired to an iPhone, any AppleWatch paired to

that iPhone can also receive a key. When a key is deleted either in the vehicle or on the

device, it can’t be restored. Keys on lost or stolen devices can be suspended and resumed,

but reprovisioning them on a new device requires a new pairing or sharing.

Car key security in iOS

Developers can support secure keyless ways to access a vehicle in a supported iPhone and

paired AppleWatch.

Owner pairing

The owner must prove possession of the vehicle (the method is dependent on the

carmaker) and can start the pairing process in the carmaker’s app using an email link

received from the carmaker or from the vehicle menu. In all cases, the owner must present

a confidential single-use pairing password to the iPhone, which is used to generate a

secure pairing channel using the SPAKE2+ protocol with the NIST P-256 curve. When using

the app or the email link, the password is automatically transferred to the iPhone, where it

must be entered manually when pairing is started from the vehicle.

Key sharing

The owner’s paired iPhone can share keys to eligible family members’ and friends’ iPhone

devices (and their paired AppleWatch devices) by sending a device-specific invitation

using iMessage and the AppleIDentity Service (IDS). All sharing commands are exchanged

using the end-to-end encrypted IDS feature. The owner’s paired iPhone keeps the IDS

channel from changing during the sharing process in order to protect against invitation

forwarding.

148Apple Platform Security

Upon acceptance of the invitation, the family member’s or friend’s iPhone creates a digital

key and sends the key creation certificate chain back to the owner’s paired iPhone to

verify that the key was created on an authentic Apple device. The owner’s paired iPhone

signs the ECC-public key of the other family member’s or friend’s iPhone and sends the

signature back to the family member’s or friend’s iPhone. The signing operation in the

owner device requires user authentication (FaceID, TouchID or passcode entry) and

a secure user intent described in Uses for FaceID and TouchID. The authorisation is

requested when sending the invitation and is stored in the secure element for consumption

when the friend device sends back the signing request. The key entitlements are provided

to the vehicle either online by the vehicle OEM server or during the first use of the shared

key on the vehicle.

Key deletion

Keys can be deleted on the keyholder device from the owner device and in the vehicle.

Deletions on the keyholder iPhone are effective immediately, even if the keyholder is using

the key. Therefore a strong warning is shown before the deletion. Deletion of keys in the

vehicle may be possible anytime or only when the vehicle is online.

In both cases, the deletion on keyholder device or vehicle is reported to a key inventory

server (KIS) on the carmaker side, which registers issued keys for a vehicle for insurance

purposes.

The owner can request a deletion from the back of the owner pass. The request is first sent

to the carmaker for key removal in the vehicle. The conditions for removing the key from

the vehicle are defined by the carmaker. Only when the key is removed in the vehicle will

the carmaker server send a remote termination request to the keyholder device.

When a key is terminated in a device, the applet that manages the digital car keys creates a

cryptographically signed termination attestation, which is used as proof of deletion by the

carmaker and used to remove the key from the KIS.

NFC standard transactions

For vehicles using an NFC key, a secure channel between the reader and an iPhone is

initiated by generating ephemeral key pairs on the reader and the iPhone side. Using a key

agreement method, a shared secret can be derived on both sides and used for generation

of a shared symmetric key using Diffie-Hellman, a key derivation function, and signatures

from the long-term key established during pairing.

The ephemeral public key generated on the vehicle side is signed with the reader’s long-

term private key, which results in an authentication of the reader by the iPhone. From the

iPhone perspective, this protocol is designed to prevent privacy-sensitive data from being

revealed to an adversary intercepting the communication.

Finally, the iPhone uses the established secure channel to encrypt its public key identifier

along with the signature computed on a reader’s data-derived challenge and some

additional app-specific data. This verification of the iPhone signature by the reader allows

the reader to authenticate the device.

149Apple Platform Security

Fast transactions

The iPhone generates a cryptogram based on a secret previously shared during a standard

transaction. This cryptogram allows the vehicle to quickly authenticate the device in

performance sensitive scenarios. Optionally, a secure channel between the vehicle and the

device is established by deriving session keys from a secret previously shared during a

standard transaction and a new ephemeral key pair. The ability of the vehicle to establish

the secure channel authenticates the vehicle to the iPhone.

BLE/UWB standard transactions

For vehicles using a UWB key, a Bluetooth LE session is established between the vehicle

and the iPhone. Similar to the NFC transaction, a shared secret is derived on both sides

and used for the establishment of a secure session. This session is used to subsequently

derive and agree a UWB Ranging Secret Key (URSK). The URSK is provided to UWB radios

in the user’s device and on the vehicle to enable accurate localisation of the user’s device

to a specific position near to or inside the vehicle. The vehicle then uses the device

position to make decisions about allowing unlocking or starting of the vehicle. URSKs have

a predefined TTL. To avoid interruption of ranging when a TTL expires, URSKs can be pre-

derived in the device SE and the vehicle HSM/SE while secure ranging is not active but BLE

is connected. This avoids the need for a standard transaction to derive a new URSK in a

time-critical situation. The pre-derived URSK can be transferred very quickly to the UWB

radios of the car and device to avoid interrupting the UWB ranging.

Privacy

The carmaker’s key inventory server (KIS) doesn’t store the device ID, SEID or AppleID. It

stores only a mutable identifier — the instance CA identifier. This identifier isn’t bound to

any private data in the device or by the server, and it’s deleted when the user wipes their

device completely (using Erase All Contents and Settings).

Adding travel and eMoney cards to Apple Wallet

In many global markets, users can add supported travel and eMoney cards to Apple Wallet

on supported models of iPhone and AppleWatch. Depending on the operator, this may

be done by transferring the value or commuter pass (or both) from a physical card into its

digital Apple Wallet representation, or by provisioning a new travel or eMoney card from

Apple Wallet or the card issuer’s app. After travel cards are added to Apple Wallet, users

can access public transport simply by holding their iPhone or AppleWatch near the card

reader. Some travel cards can also be used to make payments.

How travel and eMoney cards work

Added travel and eMoney cards are associated with a user’s iCloud account. If the user

adds more than one card to Apple Wallet, Apple or the card issuer may be able to link the

user’s personal information and associated account information between cards. Travel and

eMoney cards and transactions are protected by a set of hierarchical cryptographic keys.

During the process of transferring the balance from a physical card to Apple Wallet, users

are required to enter card-specific information. Users may also need to provide personal

information for proof of card possession. When transferring passes from iPhone to

AppleWatch, both devices must be online.

150Apple Platform Security

The balance can be recharged with funds from credit, debit and pre-paid cards through

Apple Wallet or from the travel or eMoney card issuer’s app. To understand the security of

reloading the balance when using ApplePay, see Paying with cards within apps. To learn

how the card is provisioned from within the card issuer’s app, see Adding credit or debit

cards from a card issuer’s app.

If provisioning from a physical card is supported, the travel or eMoney card issuer has the

cryptographic keys needed to authenticate the physical card and verify the user’s entered

data. After the data is verified, the system can create a Device Account Number for the

Secure Element and activate the newly added pass in Apple Wallet with the transferred

balance. For some cards, after provisioning from the physical card is complete, the

physical card is disabled.

At the end of either type of provisioning, if the card balance is stored on the device, it’s

encrypted and stored to a designated applet in the Secure Element. The operator has the

keys to perform cryptographic operations on the card data for balance transactions.

By default, travel card users benefit from the seamless Express Travel experience that

allows them to pay and go without requiring FaceID, TouchID or a passcode. Information

such as recently visited stations, transaction history and additional tickets may be

accessed by any nearby contactless card reader with Express Mode enabled. Users can

turn on the FaceID, TouchID or passcode authorisation requirement in the Wallet &

ApplePay settings by disabling Express Travel. Express mode is not supported for eMoney

cards.

As with other ApplePay cards, users can suspend or remove eMoney cards by:

• Erasing the device remotely with Find My

• Enabling Lost Mode with Find My

• Entering a mobile device management (MDM) remote wipe command

• Removing all cards from their AppleID account page

• Removing all cards from iCloud.com

• Removing all cards from Apple Wallet

• Removing the card in the issuer’s app

ApplePay servers notify the card operator to suspend or disable those cards. If a user

removes a travel or eMoney card from an online device, the balance can be recovered by

adding it back to a device signed in with the same AppleID. If a device is offline, powered

off or unusable, recovery may not be possible.

Adding travel and eMoney cards to a family member’s AppleWatch

In iOS15 and watchOS 8, the organiser of an iCloud family can add travel and eMoney

cards to their family members’ AppleWatch devices through the Watch app on their

iPhone. When provisioning one of these cards to a family member’s AppleWatch, the

watch is required to be nearby and connected to the organiser’s iPhone using Wi-Fi or

Bluetooth. Family members are required to have two-factor authentication enabled for their

AppleID for this to occur.

151Apple Platform Security

Family members can send a request to add money to a travel or eMoney card from

their AppleWatch using iMessage. The content of the message is protected by end-to-

end encryption, as described in iMessage security overview. Adding money to a card

on a family member’s AppleWatch can be done remotely using a Wi-Fi or mobile data

connection. Proximity isn’t required.

Note: This feature may not be available in all countries or regions.

Credit and debit cards

In some cities, card readers accept Chip and PIN (smart) cards to pay for public transport

journeys. When users present an EMV credit or debit card to those readers, user

authentication is required, just as with “Pay with credit and debit cards in shops”.

In iOS 12.3 or later, some existing EMV credit/debit cards in Apple Wallet can be enabled for

Express Travel. Express Travel lets users pay for a trip at supported travel operators without

requiring FaceID, TouchID or a passcode. When a user provisions an EMV credit or debit

card, the first card provisioned to Apple Wallet is enabled for Express Travel. The user can

tap the More button on the front of the card in Apple Wallet and disable Express Travel for

that card by setting Express Travel Settings to None. The user can also select a different

credit or debit card as their Express Travel card using Apple Wallet. FaceID, TouchID or a

passcode is required to re-enable or select a different card for Express Travel.

Apple Card and Apple Cash are eligible for Express Travel.

IDs in Apple Wallet

On iPhone 8 or later with iOS 15.4 or later and AppleWatch Series 4 or later with

watchOS 8.4 or later, users can add their US state ID or driving licence to Apple Wallet

and tap their iPhone or AppleWatch to seamlessly and securely present it at participating

locations.

Note: This feature is available only in participating US states.

IDs in Apple Wallet use security features built into the hardware and software of the user’s

device to help protect their identity and help keep their personal information secure.

Adding a driving licence or US state ID to Apple Wallet

On iPhone, users can simply tap the Add (+) button at the top of the screen in Apple Wallet

to begin adding their licence or ID. If users have an AppleWatch paired at the time of

setup, they are prompted to also add their driving licence or ID to their Apple Wallet on

AppleWatch.

Users are first asked to use their iPhone to scan the front and back of their physical driving

licence or state ID card. iPhone evaluates the quality and type of images provided to help

ensure they are acceptable by the state issuing authority. These identity card images are

encrypted to the state issuing authority’s key on the device and then sent to the state

issuing authority.

Next, the user is asked to complete a series of facial and head movements. These

movements are evaluated by the user’s device and by Apple to help reduce the risk

of someone using a photograph, video or mask to try to add someone else’s ID to

Apple Wallet. Results from the analysis of these movements are then sent to the state

issuing authority, but not the video of the movements themselves.

152Apple Platform Security

To help ensure that the person adding the identity card to Apple Wallet is the same person the

identity card belongs to, users are asked to take a selfie. Before the user’s photo is submitted

to the state issuing authority, Apple servers and the user’s device compare the photo with

the likeness of the person who performed the series of facial and head movements, and help

ensure that the photo being submitted is of a live person with the same likeness as that on the

ID. Once the comparison is made, the photo is encrypted on device and then sent to the state

issuing authority to be compared against their image on file for their ID.

Lastly, users are asked to perform a FaceID or TouchID authentication. The user’s device

ties this single matched FaceID or TouchID biometric to the state ID to help ensure that

only the person who added the ID to this iPhone can present it; other enrolled biometric

information cannot be used to authorise presentation of the ID. This occurs strictly on

device and isn’t sent to the state issuing authority.

The state issuing authority will receive information necessary to set up the digital ID. This

includes images of the front and back of the user’s ID, data read from the PDF417 barcode

and the selfie the user took as part of the ID verification process. The issuing state also

receives a single-digit value, used to help prevent fraud, that’s based on the user’s device

use patterns, settings data and information about their personal AppleID. It’s then ultimately

the issuing state’s decision to approve or deny the ID being added to Apple Wallet.

After the state issuing authority authorises adding the state ID or driving licence to

Apple Wallet, a key pair is generated in the Secure Element by the iPhone that anchors the

user’s ID to that specific device. If adding to AppleWatch, a key pair is generated in the

Secure Element by AppleWatch.

After the ID is on iPhone, the information reflected on the user’s ID in Apple Wallet is

stored in an encrypted format protected by the Secure Enclave.

Using a driving licence or US state ID in Apple Wallet

To use their ID in Apple Wallet, users need to authenticate with the FaceID or TouchID

device associated with the ID in Apple Wallet before iPhone presents the information to the

identity reader.

To use their ID in Apple Wallet on AppleWatch, users need to unlock their iPhone using

the associated FaceID appearance or TouchID fingerprint each time they put on their

AppleWatch. Then, they can use their ID in Apple Wallet without authenticating until

they take their AppleWatch off again. This capability leverages foundational Auto Unlock

capabilities detailed in System security for watchOS.

When users hold their iPhone or AppleWatch near the identity reader, they’ll see a prompt

on their device displaying which specific information is being requested, by whom, and

if they intend on storing it. After authorising with the associated FaceID or TouchID, the

requested identity information is released from the device.

Important: Users don’t need to unlock, show or hand over their device to present their ID.

If users have an accessibility feature like Voice Control, Switch Control or AssistiveTouch

instead of having FaceID or TouchID enabled, they can use their passcode to access and

present their information.

Transmission of identity data to the identity reader follows the ISO/IEC 18013-5 standard,

which provides for multiple security mechanisms available that are able to detect, deter

and mitigate security risks. These consist of identity data integrity and anti-forgery, device

binding, informed consent and user data confidentiality over radio links.

153Apple Platform Security

Identity data integrity and anti-forgery

IDs in Apple Wallet use an issuer-provided signature to allow any ISO/IEC 18013-5–

compliant reader to verify a user’s ID in Apple Wallet. In addition, all data elements on ID

in Apple Wallet are individually protected against forgery. This allows the identity reader to

request a specific subset of the data elements present on the ID in Apple Wallet and for the

ID in Apple Wallet to respond with that same subset, thus only sharing the requested data

and maximising the user’s privacy.

Device binding

IDs in Apple Wallet authentication uses a device signature to protect against cloning of

an ID and replay of an identity transaction. By storing the private key for ID authentication

in the iPhone device’s Secure Element, the ID is bound to the same device that the state

issuing authority created the ID for.

Informed consent

IDs in Apple Wallet reader authentication authenticates the identity reader using the

protocol defined in the ISO/IEC 18013-5 standard. During presentation, an icon derived

from the reader’s certificate is shown to them to give the user an assurance they’re

interacting with the intended party.

User data confidentiality over radio links

Session encryption helps ensure that all personally identifiable information (PII) exchanged

between the ID in Apple Wallet and that in the identity reader is encrypted. Encryption

is performed by the application layer. The security of session encryption is therefore not

reliant on the security provided by the transmission layer (for example, NFC, Bluetooth and

Wi-Fi).

IDs in Apple Wallet help keep users’ information private

IDs in Apple Wallet adhere to the “device retrieval” process outlined in ISO/IEC 18013-5.

Device retrieval obviates the need to make server calls during presentation, thereby

protecting users from being tracked by Apple and the issuer.

154Apple Platform Security

iMessage

iMessage security overview

Apple iMessage is a messaging service for iOS and iPadOS devices, AppleWatch and Mac

computers. iMessage supports text and attachments such as photos, contacts, locations,

links and attachments directly on to a message, such as a thumbs up icon. Messages

appear on all of a user’s registered devices so that a conversation can be continued from

any of the user’s devices. iMessage makes extensive use of the Apple Push Notification

service (APNs). Apple doesn’t log the contents of messages or attachments, which are

protected by end-to-end encryption so no one but the sender and receiver can access

them. Apple can’t decrypt the data.

When a user turns on iMessage on a device, the device generates encryption and signing

pairs of keys for use with the service. For encryption, there is an encryption RSA 1280-

bit key as well as an encryption EC 256-bit key on the NIST P-256 curve. For signatures,

Elliptic Curve Digital Signature Algorithm (ECDSA) 256-bit signing keys are used. The

private keys are saved in the device’s keychain and only available after first unlock. The

public keys are sent to AppleIDentity Service (IDS) where they are associated with the

user’s phone number or email address, along with the device’s APNs address.

As users enable additional devices for use with iMessage, their encryption and signing

public keys, APNs addresses and associated phone numbers are added to the directory

service. Users can also add more email addresses which are verified by sending a

confirmation link. Phone numbers are verified by the network provider's network and SIM.

With some networks, this requires using SMS (the user is presented with a confirmation

dialogue if the SMS isn’t zero rated). Phone number verification may be required for several

system services in addition to iMessage, such as FaceTime and iCloud. All the user’s

registered devices display an alert message when a new device, phone number or email

address is added.

How iMessage sends and receives messages securely

Users start a new iMessage conversation by entering an address or name. If they enter

a phone number or email address, the device contacts the AppleIDentity Service (IDS)

to retrieve the public keys and APNs addresses for all the devices associated with the

addressee. If the user enters a name, the device first uses the user’s Contacts app to

gather the phone numbers and email addresses associated with that name and then gets

the public keys and APNs addresses from IDS.

155Apple Platform Security

The user’s outgoing message is individually encrypted for each of the receiver’s devices.

The public encryption keys and signing keys of the receiving devices are retrieved from

IDS. For each receiving device, the sending device generates a random 88-bit value and

uses it as an HMAC-SHA256 key to construct a 40-bit value derived from the sender and

receiver public key and the plaintext. The concatenation of the 88-bit and 40-bit values

makes a 128-bit key, which encrypts the message with it using AES in Counter (CTR)

Mode. The 40-bit value is used by the receiver side to verify the integrity of the decrypted

plaintext. This per-message AES key is encrypted using RSA-OAEP to the public key of

the receiving device. The combination of the encrypted message text and the encrypted

message key is then hashed with SHA-1 and the hash is signed with the Elliptic Curve

Digital Signature Algorithm (ECDSA) using the sending device’s private signing key. In

iOS13 or later and iPadOS 13.1 or later, devices may use an Elliptic Curve Integrated

Encryption Scheme (ECIES) encryption instead of RSA encryption.

The resulting messages, one for each receiving device, consist of the encrypted message

text, the encrypted message key and the sender’s digital signature. They are then

dispatched to the APNs for delivery. Metadata, such as the timestamp and APNs routing

information, isn’t encrypted. Communication with APNs is encrypted using a forward-

secret TLS channel.

APNs can only relay messages up to 4 or 16KB in size, depending on the iOS or iPadOS

version. If the message text is too long or if an attachment such as a photo is included, the

attachment is encrypted using AES in CTR mode with a randomly generated 256-bit key

and uploaded to iCloud. The AES key for the attachment, its Uniform Resource Identifier

(URI) and an SHA-1 hash of its encrypted form are then sent to the recipient as the

contents of an iMessage, with their confidentiality and integrity protected through normal

iMessage encryption, as shown in the following diagram.

156Apple Platform Security

For group conversations, this process is repeated for each recipient and their devices.

On the receiving side, each device receives its copy of the message from APNs and, if

necessary, retrieves the attachment from iCloud. The incoming phone number or email

address of the sender is matched to the receiver’s contacts so that a name can be

displayed when possible.

As with all push notifications, the message is deleted from APNs when it’s delivered. Unlike

other APNs notifications, however, iMessage messages are queued for delivery to offline

devices. Messages are stored on Apple servers for up to 30 days.

Secure iMessage name and photo sharing

iMessage Name and Photo Sharing allows a user to share a Name and Photo using

iMessage. The user may select their My Card information, or customise the name and

include any image they choose. iMessage Name and Photo sharing uses a two-stage

system to distribute the name and photo.

The data is subdivided into fields, each encrypted and authenticated separately as well as

authenticated together with the below process. There are three fields:

• Name

• Photo

• Photo filename

One of the first steps in creating the data is to randomly generate a record 128-bit key

on the device. This record key is then derived with HKDF-HMAC-SHA256 to create three

subkeys: Key 1:Key 2:Key 3 = HKDF(record key, “nicknames”). For each field, a random

96-bit Initialisation Vector (IV) is generated and the data is encrypted using AES-CTR and

Key 1. A message authentication code (MAC) is then computed with HMAC-SHA256 using

Key 2 and covering the field name, the field IV and the field ciphertext. Finally, the set

of individual field MAC values are concatenated and their MAC is computed with HMAC-

SHA256 using Key 3. The 256-bit MAC is stored alongside the encrypted data. The first

128 bits of this MAC is used as RecordID.

This encrypted record is then stored in the CloudKit public database under the RecordID.

This record is never mutated and when the user chooses to change their name and photo,

a new encrypted record is generated each time. When user 1 chooses to share their

name and photo with user 2, they send the record key along with the recordID inside their

iMessage payload, which is encrypted.

When user 2’s device receives this iMessage payload, it notices that the payload contains a

Nickname and Photo recordID and key. User 2’s device then goes out to the public CloudKit

database to retrieve the encrypted name and photo at the record ID and sends it across

using iMessage.

After the message is retrieved, user 2’s device decrypts the payload and verifies the

signature using the recordID itself. If this passes, user 2 is presented with the name and

photo and they can choose to add this to their contacts or use it for Messages.

157Apple Platform Security

Secure Apple Messages for Business

Apple Messages for Business is a messaging service that allows users to communicate

with businesses using the Messages app. With Apple Messages for Business, the user is

always in control of the conversation. They can also delete the conversation and block

the business from messaging them in the future. For privacy, the business doesn’t receive

the user’s phone number, email address or iCloud account information. Instead, a custom

unique identifier called the Opaque ID is generated by the AppleIDentity Service (IDS)

and shared with the business. The Opaque ID is unique to the relationship between the

user’s AppleID and the business’s Business ID. A user has a different Opaque ID for every

business they contact using Apple Messages for Business. The user decides if and when

to share personal identifying information with the business and the Apple Messages for

Business service never stores conversation history.

Apple Messages for Business supports Managed AppleIDs from Apple Business Manager

and determines whether they are enabled for iMessage and FaceTime in Apple School

Manager.

Messages sent to the business are encrypted between the user’s device and Apple’s

messaging servers using the same security and Apple messaging servers as iMessages.

Apple messaging servers decrypt these messages in RAM and relay them to the business

over an encrypted link using TLS 1.2. Messages are never stored in unencrypted form while

transiting through the Apple Messages for Business service. Businesses’ replies are also

sent using TLS 1.2 to the Apple messaging servers, where they are encrypted using the

unique public keys of each recipient device.

If user devices are online, the message is delivered immediately and isn’t cached on the

Apple messaging servers. If a user’s device isn’t online, the encrypted message is cached

for up to 30 days to enable the user to receive it when the device is back online. As soon

as the device is back online, the message is delivered and deleted from cache. After 30

days, an undelivered cached message expires and is permanently deleted.

FaceTime security

FaceTime is Apple’s video and audio calling service. Like iMessage, FaceTime calls use

the Apple Push Notification service (APNs) to establish an initial connection to the user’s

registered devices. The audio/video contents of FaceTime calls are protected by end-

to-end encryption, so no one but the sender and receiver can access them. Apple can’t

decrypt the data.

The initial FaceTime connection is made through an Apple server infrastructure that relays

data packets between the users’ registered devices. Using APNs notifications and Session

Traversal Utilities for NAT (STUN) messages over the relayed connection, the devices

verify their identity certificates and establish a shared secret for each session. The shared

secret is used to derive session keys for media channels streamed using the Secure Real-

time Transport Protocol (SRTP). SRTP packets are encrypted using AES256 in Counter

Mode and authenticated with HMAC-SHA1. After the initial connection and security setup,

FaceTime uses STUN and Internet Connectivity Establishment (ICE) to establish a peer-to-

peer connection between devices, if possible.

158Apple Platform Security

Group FaceTime extends FaceTime to support up to 33 concurrent participants. As

with classic one-to-one FaceTime, calls are end-to-end encrypted among the invited

participants’ devices. Even though Group FaceTime reuses much of the infrastructure and

design of one-to-one FaceTime, these group calls feature a key-establishment mechanism

built on top of the authenticity provided by AppleIDentity Service (IDS). This protocol

provides forward secrecy, meaning that the compromise of a user’s device won’t leak

the contents of past calls. Session keys are wrapped using AES-SIV and are distributed

between participants using an ECIES construction with ephemeral P-256 ECDH keys.

When a new phone number or email address is added to an ongoing Group FaceTime call,

active devices establish new media keys and never share previously used keys with the

newly invited devices.

Find My

Find My security

The Find My app for Apple devices is built on a foundation of advanced public key

cryptography.

Overview

The Find My app combines Find My iPhone and Find My Friends into a single app in iOS,

iPadOS and macOS. Find My can help users locate a missing device, even an offline Mac.

An online device can simply report its location to the user via iCloud. Find My works offline

by sending out short range Bluetooth signals from the missing device that can be detected

by other Apple devices in use nearby. Those nearby devices then relay the detected

location of the missing device to iCloud so users can locate it in the Find My app — all

while protecting the privacy and security of all the users involved. Find My even works with

a Mac that is offline and asleep.

Using Bluetooth and the hundreds of millions of iOS, iPadOS and macOS devices in active

use around the world, a user can locate their missing device even if it can’t connect to

a Wi-Fi or mobile data network. Any iOS, iPadOS or macOS device with “offline finding”

enabled in Find My settings can act as a “finder device”. This means the device can detect

the presence of another missing offline device using Bluetooth and then use its network

connection to report an approximate location back to the owner. When a device has offline

finding enabled, it also means that it can be located by other participants in the same way.

This entire interaction is end-to-end encrypted, anonymous, and designed to be battery

and data efficient. There is minimal impact on battery life and data plan usage, and user

privacy is better protected.

Note: Find My may not be available in all countries or regions.

159Apple Platform Security

End-to-end encryption

Find My is built on a foundation of advanced public key cryptography. When offline

finding is enabled in Find My settings, an elliptic curve (EC) P-224 private encryption

key pair noted {d,P} is generated directly on the device where d is the private key and P

is the public key. Additionally, a 256-bit secret SK0 and a counter i is initialised to zero.

This private key pair and the secret are never sent to Apple and are synced only among

the user’s other devices in an end-to-end encrypted manner using iCloud Keychain. The

secret and the counter are used to derive the current symmetric key SKi with the following

recursive construction: SKi = KDF(SKi-1, “update”).

Based on the key SKi, two large integers ui and vi are computed with (ui,vi) = KDF(SKi,

“diversify”). Both the P-224 private key denoted d and corresponding public key referred

to as P are then derived using an affine relation involving the two integers to compute a

short-lived key pair: The derived private key is di, where di = ui * d + vi (modulo the order of

the P-224 curve) and the corresponding public part is Pi and verifies that Pi = ui*P + vi*G.

When a device goes missing and can’t connect to Wi-Fi or mobile data — for example,

a MacBook Pro is left on a park bench — it begins periodically broadcasting the derived

public key Pi for a limited period of time in a Bluetooth payload. By using P-224, the public

key representation can fit into a single Bluetooth payload. The surrounding devices can

then help in the finding of the offline device by encrypting their location to the public

key. Approximately every 15 minutes, the public key is replaced by a new one using an

incremented value of the counter and the process above so that the user can’t be tracked

by a persistent identifier. The derivation mechanism is designed to prevent the various

public keys Pi from being linked to the same device.

Keeping users and devices anonymous

In addition to making sure that location information and other data are fully encrypted,

participants’ identities remain private from each other and from Apple. The traffic sent

to Apple by finder devices contains no authentication information in the contents or

headers. As a result, Apple doesn’t know who the finder is or whose device has been

found. Furthermore, Apple doesn’t log information that would reveal the identity of the

finder and retains no information that would allow anyone to correlate the finder and owner.

The device owner receives only the encrypted location information that’s decrypted and

displayed in the Find My app with no indication as to who found the device.

160Apple Platform Security

Using Find My to locate missing Apple devices

Any Apple devices within Bluetooth range that have offline finding enabled can detect

a signal from another Apple device configured to allow Find My and read the current

broadcast key Pi. Using an ECIES construction and the public key Pi from the broadcast,

the finder devices encrypt their current location information and relay it to Apple. The

encrypted location is associated with a server index which is computed as the SHA256

hash of the P-224 public key Pi obtained from the Bluetooth payload. Apple never has the

decryption key, so Apple can’t read the location encrypted by the finder. The owner of the

missing device can reconstruct the index and decrypt the encrypted location.

When trying to locate the missing device, an expected range of counter values is estimated

for the location search period. With the knowledge of the original private P-224 key d

and secret values SKi in the range of counter values of the search period, the owner can

then reconstruct the set of values {di, SHA256(Pi)} for the entire search period. The owner

device used to locate the missing device can then perform queries to the server using the

set of index values SHA256(Pi) and download the encrypted locations from the server. The

Find My app then locally decrypts the encrypted locations with the matching private keys

di and shows an approximate location of the missing device in the app. Location reports

from multiple finder devices are combined by the owner’s app to generate a more precise

location.

161Apple Platform Security

Locating devices that are offline

If a user has Find My iPhone enabled on their device, offline finding is enabled by default

when they upgrade a device to iOS13 or later, iPadOS 13.1 or later and macOS 10.15 or

later. This is designed to ensure that every user has the best possible chance to locate

their device if it goes missing. However, if at any time the user prefers not to participate,

they can disable offline finding in Find My settings on their device. When offline finding is

disabled, the device no longer acts as a finder nor is it detectable by other finder devices.

However, the user can still locate the device as long as it can connect to a Wi-Fi or mobile

network.

When a missing offline device is located, the user receives a notification and email

message to let them know the device has been found. To view the location of the missing

device, the user opens the Find My app and selects the Devices tab. Rather than showing

the device on a blank map as it would have prior to the device being located, Find My

shows a map location with an approximate address and information on how long ago

the device was detected. If more location reports come in, the current location and time

stamp both update automatically. Although users can’t play a sound on an offline device or

erase it remotely, they can use the location information to retrace their steps or take other

actions to help them recover it.

Continuity

Continuity security overview

Continuity takes advantage of technologies like iCloud, Bluetooth and Wi-Fi to enable users

to continue an activity from one device to another, make and receive phone calls, send and

receive text messages, and share a mobile data internet connection.

Handoff security

Apple handles handoffs securely, whether from one device to another, between a native

app and a website — even handoffs of large amounts of data.

How Handoff works securely

With Handoff, when a user’s iOS, iPadOS and macOS devices are near each other, the user

can automatically pass whatever they’re working on from one device to the other. Handoff

lets the user switch devices and instantly continue working.

When a user signs in to iCloud on a second Handoff-capable device, the two devices

establish a Bluetooth Low Energy (BLE) 4.2 pairing out-of-band using APNs. The individual

messages are encrypted much like messages in iMessage are. After the devices are paired,

each device generates a symmetric 256-bit AES key that gets stored in the device’s

keychain. This key can encrypt and authenticate the BLE advertisements that communicate

the device’s current activity to other iCloud-paired devices using AES256 in GCM mode,

with replay protection measures.

162Apple Platform Security

The first time a device receives an advertisement from a new key, it establishes a BLE

connection to the originating device and performs an advertisement encryption key

exchange. This connection is secured using standard BLE 4.2 encryption as well as

encryption of the individual messages, which is similar to how iMessage is encrypted. In

some situations, these messages are sent using APNs instead of BLE. The activity payload

is protected and transferred in the same way as an iMessage.

Handoff between native apps and websites

Handoff allows an iOS, iPadOS or macOS native app to resume user activity on a web page

in domains legitimately controlled by the app developer. It also allows the native app user

activity to be resumed in a web browser.

To help prevent native apps from claiming to resume websites not controlled by the

developer, the app must demonstrate legitimate control over the web domains it wants to

resume. Control over a website domain is established using the mechanism for shared web

credentials. For details, see App access to saved passwords. The system must validate an

app’s domain name control before the app is permitted to accept user activity Handoff.

The source of a web page Handoff can be any browser that has adopted the Handoff APIs.

When the user views a web page, the system advertises the domain name of the web page

in the encrypted Handoff advertisement bytes. Only the user’s other devices can decrypt

the advertisement bytes.

On a receiving device, the system detects that an installed native app accepts Handoff

from the advertised domain name and displays that native app icon as the Handoff option.

When launched, the native app receives the full URL and the title of the web page. No other

information is passed from the browser to the native app.

In the opposite direction, a native app may specify a fallback URL when a Handoff receiving

device doesn’t have the same native app installed. In this case, the system displays the

user’s default browser as the Handoff app option (if that browser has adopted Handoff

APIs). When Handoff is requested, the browser is launched and given the fallback URL

provided by the source app. There is no requirement that the fallback URL be limited to

domain names controlled by the native app developer.

Handoff of larger data

In addition to using the basic feature of Handoff, some apps may elect to use APIs that

support sending larger amounts of data over Apple-created peer-to-peer Wi-Fi technology

(much like AirDrop). For example, the Mail app uses these APIs to support handoff of a mail

draft, which may include large attachments.

When an app uses these APIs, the exchange between the two devices starts off just as

in Handoff. But after receiving the initial payload using Bluetooth Low Energy (BLE), the

receiving device initiates a new connection over Wi-Fi. This connection is encrypted (with

TLS), and it derives trust through an identity shared through iCloud Keychain. The identity

in the certificates is verified against the user’s identity. Further payload data is sent over

this encrypted connection until the transfer is complete.

163Apple Platform Security

Universal Clipboard

Universal Clipboard leverages Handoff to securely transfer the content of a user’s

clipboard across devices so they can copy on one device and paste on another. Content is

protected in the same way as other Handoff data and is shared by default with Universal

Clipboard unless the app developer chooses to disallow sharing.

Apps have access to clipboard data regardless of whether the user has pasted the

clipboard into the app. With Universal Clipboard, this data access extends to apps on the

user’s other devices (as established by their iCloud sign-in).

iPhone mobile call relay security

When a user’s Mac, iPad, iPodtouch or HomePod is on the same Wi-Fi network as their

iPhone, it can make and receive phone calls using the mobile data connection on iPhone.

Configuration requires the devices to be signed in to both iCloud and FaceTime using the

same AppleID account.

When an incoming call arrives, all configured devices are notified using the Apple Push

Notification service (APNs), with each notification using the same end-to-end encryption

as iMessage. Devices that are on the same network present the incoming call notification

user interface. When the user answers the call, the audio is seamlessly transmitted from

the user’s iPhone using a secure peer-to-peer connection between the two devices.

When a call is answered on one device, ringing of nearby iCloud-paired devices is

terminated by briefly advertising using Bluetooth Low Energy (BLE). The advertising bytes

are encrypted using the same method as Handoff advertisements.

Outgoing calls are also relayed to iPhone using APNs and audio is similarly transmitted

over the secure peer-to-peer link between devices. Users can disable phone call relay on a

device by turning off iPhone Mobile Calls in FaceTime settings.

iPhone Text Message Forwarding security

Text Message Forwarding automatically sends SMS text messages received on an iPhone to

a user’s enrolled iPad, iPodtouch or Mac. Each device must be signed in to the iMessage

service using the same AppleID account. When Text Message Forwarding is turned on,

enrolment is automatic on devices within a user’s circle of trust if two-factor authentication

is enabled. Otherwise, enrolment is verified on each device by entering a random six-digit

numeric code generated by iPhone.

After devices are linked, iPhone encrypts and forwards incoming SMS text messages

to each device, utilising the methods described in iMessage security overview. Replies

are sent back to iPhone using the same method and then iPhone sends the reply as a

text message using the network provider’s SMS transmission mechanism. Text Message

Forwarding can be turned on or off in Messages settings.

164Apple Platform Security

Instant Hotspot security

Instant Hotspot connects other Apple devices to a personal iOS or iPadOS hotspot. iOS and

iPadOS devices that support Instant Hotspot use Bluetooth Low Energy (BLE) to discover

and communicate to all devices that have signed in to the same individual iCloud account

or accounts used with Family Sharing (in iOS13 and iPadOS). Compatible Mac computers

with OS X 10.10 or later use the same technology to discover and communicate with Instant

Hotspot iOS and iPadOS devices.

Initially, when a user enters Wi-Fi settings on a device, it emits a BLE advertisement

containing an identifier that all devices signed in to the same iCloud account agree upon.

The identifier is generated from a DSID (Destination Signaling Identifier) that’s tied to the

iCloud account and rotated periodically. When other devices signed in to the same iCloud

account are in close proximity and support Personal Hotspot, they detect the signal and

respond, indicating the availability to use Instant Hotspot.

When a user who isn’t part of Family Sharing chooses an iPhone or iPad for Personal

Hotspot, a request to turn on Personal Hotspot is sent to that device. The request is sent

across a link that is encrypted using BLE encryption, and the request is encrypted in a

fashion similar to iMessage encryption. The device then responds across the same BLE link

using the same per-message encryption with Personal Hotspot connection information.

For users that are part of Family Sharing, Personal Hotspot connection information is

securely shared using a mechanism similar to that used by HomeKit devices to sync

information. Specifically, the connection that shares hotspot information between users is

secured with an ECDH (Curve25519) ephemeral key that is authenticated with the users’

respective device-specific Ed25519 public keys. The public keys used are those that had

previously synced between the members of Family Sharing using IDS when the Family

Share was established.

165Apple Platform Security

Network security

Network security overview

In addition to the built-in safeguards Apple uses to protect data stored on Apple devices,

there are many measures organisations can take to keep information secure as it travels to

and from a device. All these safeguards and measures fall under network security.

Because users must be able to access corporate networks from anywhere in the world,

it’s important to help ensure that they are authorised and that their data is protected

during transmission. To accomplish these security objectives, iOS, iPadOS and macOS

integrate proven technologies and the latest standards for both Wi-Fi and mobile data

network connections. That’s why our operating systems use — and provide developer

access to — standard networking protocols for authenticated, authorised and encrypted

communications.

TLS security

iOS, iPadOS and macOS support Transport Layer Security (TLS 1.0, TLS 1.1, TLS 1.2,

TLS 1.3) and Datagram Transport Layer Security (DTLS). The TLS protocol supports

both AES128 and AES256, and prefers cipher suites with forward secrecy. Internet apps

such as Safari, Calendar and Mail automatically use this protocol to enable an encrypted

communication channel between the device and network services. High-level APIs (such

as CFNetwork) make it easy for developers to adopt TLS in their apps, while low-level APIs

(such as Network.framework) provide fine-grained control. CFNetwork disallows SSL 3, and

apps that use WebKit (such as Safari) are prohibited from making an SSL 3 connection.

In iOS11 or later and macOS 10.13 or later, SHA-1 certificates are no longer allowed for

TLS connections unless trusted by the user. Certificates with RSA keys shorter than 2048

bits are also disallowed. The RC4 symmetric cipher suite is deprecated in iOS10 and

macOS 10.12. By default, TLS clients or servers implemented with SecureTransport APIs

don’t have RC4 cipher suites enabled and are unable to connect when RC4 is the only

cipher suite available. To be more secure, services or apps that require RC4 should be

upgraded to use secure cipher suites. In iOS 12.1, certificates issued after 15 October 2018

from a system-trusted root certificate must be logged in a trusted Certificate Transparency

log to be allowed for TLS connections. In iOS 12.2, TLS 1.3 is enabled by default for

Network.framework and NSURLSession APIs. TLS clients using the SecureTransport APIs

can’t use TLS 1.3.

166Apple Platform Security

App Transport Security

App Transport Security provides default connection requirements so that apps adhere

to best practices for secure connections when using NSURLConnection, CFURL or

NSURLSession APIs. By default, App Transport Security limits cipher selection to include

only suites that provide forward secrecy, specifically:

• ECDHE_ECDSA_AES and ECDHE_RSA_AES in Galois/Counter Mode (GCM)

• Cipher Block Chaining (CBC) mode

Apps are able to disable the forward secrecy requirement per domain, in which case RSA_

AES is added to the set of available ciphers.

Servers must support TLS 1.2 and forward secrecy, and certificates must be valid and

signed using SHA256 or stronger with a minimum 2048-bit RSA key or 256-bit elliptic

curve key.

Network connections that don’t meet these requirements will fail unless the app

overrides App Transport Security. Invalid certificates always result in a hard failure and no

connection. App Transport Security is automatically applied to apps that are compiled for

iOS9 or later and macOS 10.11 or later.

Certificate validity checking

Evaluating the trusted status of a TLS certificate is performed in accordance with

established industry standards, as set out in RFC 5280, and incorporates emerging

standards such as RFC 6962 (Certificate Transparency). In iOS11 or later and macOS 10.13

or later, Apple devices are periodically updated with a current list of revoked and

constrained certificates. The list is aggregated from certificate revocation lists (CRLs),

which are published by each of the built-in root certificate authorities trusted by Apple,

as well as by their subordinate CA issuers. The list may also include other constraints

at Apple’s discretion. This information is consulted whenever a network API function is

used to make a secure connection. If there are too many revoked certificates from a CA

to list individually, a trust evaluation may instead require that an online certificate status

response (OCSP) is needed, and if the response isn’t available, the trust evaluation will fail.

IPv6 security

All Apple operating systems support IPv6, implementing several mechanisms to protect

the privacy of users and the stability of the networking stack. When Stateless Address

Autoconfiguration (SLAAC) is used, the IPv6 addresses of all interfaces are generated in

a way that helps prevent tracking devices across networks, and at the same time allows

for a good user experience by ensuring address stability when no network changes

take place. The address generation algorithm is based on cryptographically generated

addresses as of RFC 3972, enhanced by an interface-specific modifier to warrant that even

different interfaces on the same network eventually have different addresses. Furthermore,

temporary addresses are created with a preferred lifetime of 24 hours, and these are

used by default for any new connections. Aligned with the Private Wi-Fi address feature

introduced in iOS 14, iPadOS14 and watchOS 7, a unique link-local address is generated

for every Wi-Fi network that a device joins. The network’s SSID is incorporated as an

additional element for the address generation, similar to the Network_ID parameter as of

RFC 7217. This approach is used in iOS 14, iPadOS14 and watchOS 7.

167Apple Platform Security

To protect against attacks based on IPv6 extension headers and fragmentation, Apple

devices implement protection measures specified in RFC 6980, RFC 7112 and RFC 8021.

Among other measures, these inhibit attacks where the upper-layer header can be found

only in the second fragment (as shown below), which in turn could cause ambiguities for

security controls like stateless packet filters.

In addition, to help ensure the reliability of the IPv6 stack of Apple operating systems,

Apple devices enforce various limits on IPv6-related data structures, such as the number

of prefixes per interface.

Virtual private network (VPN) security

Secure network services like virtual private networking typically require minimal setup and

configuration to work with iOS, iPadOS and macOS devices.

Protocols supported

These devices work with VPN servers that support the following protocols and

authentication methods:

• IKEv2/IPsec with authentication by shared secret, RSA Certificates, Elliptic Curve Digital

Signature Algorithm (ECDSA) Certificates, EAP-MSCHAPv2 or EAP-TLS

• SSL-VPN using the appropriate client app from the AppStore

• L2TP/IPsec with user authentication by MS-CHAPV2 password and machine

authentication by shared secret (iOS, iPadOS and macOS) and RSA SecurID or

CRYPTOCard (macOS only)

• Cisco IPsec with user authentication by password, RSA SecurID or CRYPTOCard, and

machine authentication by shared secret and certificates (macOS only)

168Apple Platform Security

VPN deployments supported

iOS, iPadOS and macOS support the following:

• VPN On Demand: For networks that use certificate-based authentication. IT policies

specify which domains require a VPN connection by using a VPN configuration profile.

• Per App VPN: For facilitating VPN connections on a much more granular basis. Mobile

device management (MDM) solutions can specify a connection for each managed app

and specific domains in Safari. This helps ensure that secure data always goes to and

from the corporate network — and that a user’s personal data doesn’t.

iOS and iPadOS support the following:

• Always On VPN: For devices managed through an MDM solution and supervised

using Apple Configurator for Mac, Apple School Manager or Apple Business Manager.

Always On VPN eliminates the need for users to turn on VPN to enable protection when

connecting to mobile and Wi-Fi networks. It also gives an organisation full control

over device traffic by tunnelling all IP traffic back to the organisation. The default

exchange of parameters and keys for the subsequent encryption, IKEv2, secures traffic

transmission with data encryption. The organisation can monitor and filter traffic to

and from its devices, secure data within its network and restrict device access to the

internet.

Wi-Fi security

Secure access to wireless networks

All Apple platforms support industry-standard Wi-Fi authentication and encryption

protocols to provide authenticated access and confidentiality when connecting to the

following secure wireless networks:

• WPA2 Personal

• WPA2 Enterprise

• WPA2/WPA3 Transitional

• WPA3 Personal

• WPA3 Enterprise

• WPA3 Enterprise 192-bit security

WPA2 and WPA3 authenticate each connection and provide 128-bit AES encryption to

help ensure confidentiality of data sent over the air. This grants users the highest level

of assurance that their data remains protected when they’re sending and receiving

communications over a Wi-Fi network connection.

169Apple Platform Security

WPA3 support

WPA3 is supported on the following Apple devices:

• iPhone 7 or later

• iPad 5th generation or later

• AppleTV 4K or later

• AppleWatch series 3 or later

• Mac computers (late 2013 or later, with 802.11ac or later)

Newer devices support authentication with WPA3 Enterprise 192-bit security, including

support for 256-bit AES encryption when connecting to compatible wireless access

points (APs). This provides even stronger confidentiality protections for traffic sent

over the air. WPA3 Enterprise 192-bit security is supported on iPhone 11, iPhone 11 Pro,

iPhone 11 Pro Max, and later iOS and iPadOS devices.

PMF support

In addition to protecting data sent over the air, Apple platforms extend WPA2 and WPA3

level protections to unicast and multicast management frames through the Protected

Management Frame (PMF) service defined in 802.11w. PMF support is available on the

following Apple devices:

• iPhone 6 or later

• iPad Air 2 or later

• AppleTV HD or later

• AppleWatch series 3 or later

• Mac computers (late 2013 or later, with 802.11ac or later)

With support for 802.1X, Apple devices can be integrated into a broad range of RADIUS

authentication environments. 802.1X wireless authentication methods supported include

EAP-TLS, EAP-TTLS, EAP-FAST, EAP-SIM, PEAPv0 and PEAPv1.

Platform protections

Apple operating systems protect the device from vulnerabilities in network processor

firmware. This means network controllers with Wi-Fi have limited access to Application

Processor memory.

• When USB or SDIO (Secure Digital Input Output) is used to interface with the

network processor, the network processor can’t initiate direct memory access (DMA)

transactions to the Application Processor.

• When PCIe is used, each network processor is on its own isolated PCIe bus. An Input/

Output Memory Management Unit (IOMMU) on each PCIe bus further limits the network

processor’s DMA access to only memory and resources containing its network packets

and control structures.

170Apple Platform Security

Deprecated protocols

Apple products support the following deprecated Wi-Fi authentication and encryption

protocols:

• WEP Open, with both 40-bit and 104-bit keys

• WEP Shared, with both 40-bit and 104-bit keys

• Dynamic WEP

• Temporal Key Integrity Protocol (TKIP)

• WPA

• WPA/WPA2 Transitional

These protocols are no longer considered secure and their use is strongly discouraged

for compatibility, reliability, performance and security reasons. They are supported for

backward compatibility purposes only and may be removed in future software versions.

It’s recommended that all Wi-Fi implementations be migrated to WPA3 Personal or WPA3

Enterprise, to provide the most robust, secure and compatible Wi-Fi connections possible.

Wi-Fi privacy

MAC address randomisation

Apple platforms use a randomised media access control address (MAC address) when

performing Wi-Fi scans when not associated with a Wi-Fi network. These scans can be

performed to find and connect to a known Wi-Fi network or to assist Location Services for

apps that use geofences, such as location-based reminders or fixing a location in Apple

Maps. Note that Wi-Fi scans that happen while trying to connect to a preferred Wi-Fi

network aren’t randomised. Wi-Fi MAC address randomisation support is available on

iPhone 5 or later.

Apple platforms also use a randomised MAC address when conducting enhanced Preferred

Network Offload (ePNO) scans when a device isn’t associated with a Wi-Fi network or its

processor is asleep. ePNO scans are run when a device uses Location Services for apps

that use geofences, such as location-based reminders that determine whether the device

is near a specific location.

Because a device’s MAC address changes when disconnected from a Wi-Fi network,

it can’t be used to persistently track a device by passive observers of Wi-Fi traffic,

even when the device is connected to a mobile network. Apple has informed Wi-Fi

manufacturers that iOS and iPadOS Wi-Fi scans use a randomised MAC address and that

neither Apple nor manufacturers can predict these randomised MAC addresses.

In iOS14 or later, iPadOS14 or later, and watchOS7 or later, when an iPhone, iPad,

iPodtouch or AppleWatch connects to a Wi-Fi network, it identifies itself with a unique

(random) MAC address per network. This feature can be disabled either by the user or by

using a new option in the Wi-Fi payload. Under certain circumstances, the device will fall

back to the actual MAC address.

For more information, see the Apple Support article Use private Wi-Fi addresses on iPhone,

iPad, iPodtouch and AppleWatch.

171Apple Platform Security

Wi-Fi frame sequence number randomisation

Wi-Fi frames include a sequence number which is used by the low-level 802.11 protocol

to enable efficient and reliable Wi-Fi communications. Because these sequence numbers

increment on each transmitted frame, they could be used to correlate information

transmitted during Wi-Fi scans with other frames transmitted by the same device.

To guard against this, Apple devices randomise the sequence numbers whenever a MAC

address is changed to a new randomised address. This includes randomising the sequence

numbers for each new scan request that’s initiated while the device is unassociated. This

randomisation is supported on the following devices:

• iPhone 7 or later

• iPad 5th generation or later

• AppleTV 4K or later

• AppleWatch series 3 or later

• iMac Pro (Retina 5K, 27-inch, 2017) or later

• MacBook Pro (13-inch, 2018) or later

• MacBook Pro (15-inch, 2018) or later

• MacBook Air (Retina, 13-inch, 2018) or later

• Mac mini (2018) or later

• iMac (Retina 4K, 21.5-inch, 2019) or later

• iMac (Retina 5K, 27-inch, 2019) or later

• Mac Pro (2019) or later

Wi-Fi connections

Apple generates randomised MAC addresses for the Peer-to-Peer Wi-Fi connections

that are used for AirDrop and AirPlay. Randomised addresses are also used for Personal

Hotspot in iOS and iPadOS (with a SIM card) and Internet Sharing in macOS.

New random addresses are generated whenever these network interfaces are started, and

unique addresses are independently generated for each interface as needed.

Hidden networks

Wi-Fi networks are identified by their network name, known as a service set identifier

(SSID). Some Wi-Fi networks are configured to hide their SSID, which results in the wireless

access point not broadcasting the network’s name. These are known as hidden networks.

iPhone 6s and later devices automatically detect when a network is hidden. If a network is

hidden, the iOS or iPadOS device sends a probe with the SSID included in the request—

not otherwise. This helps prevent the device from broadcasting the name of previously

hidden networks a user was connected to, thereby further ensuring privacy.

172Apple Platform Security

Bluetooth security

There are two types of Bluetooth in Apple devices, Bluetooth Classic and Bluetooth Low

Energy (BLE). The Bluetooth security model for both versions includes the following

distinct security features:

• Pairing: The process for creating one or more shared secret keys

• Bonding: The act of storing the keys created during pairing for use in subsequent

connections to form a trusted device pair

• Authentication: Verifying that the two devices have the same keys

• Encryption: Message confidentiality

• Message integrity: Protection against message forgeries

• Secure Simple Pairing: Protection against passive eavesdropping and protection against

man-in-the-middle attacks

Bluetooth version 4.1 added the Secure Connections feature to Bluetooth Classic (BR/EDR)

physical transport.

The security features for each type of Bluetooth are listed below.

Support Bluetooth Classic Bluetooth Low Energy

Pairing P-256 elliptic curve FIPS-approved algorithms (AES-CMAC

and P-256 elliptic curve)

Bonding Pairing information stored in a

secure location in iOS, iPadOS,

macOS, tvOS and watchOS devices

Pairing information stored in a secure

location in iOS, iPadOS, macOS, tvOS

and watchOS devices

X authentication. FIPS-approved algorithms (HMAC-

SHA256 and AES-CTR)

FIPS-approved algorithms

Encryption AES-CCM cryptography, performed

in the Controller

AES-CCM cryptography, performed in

the Controller

Message integrity AES-CCM, used for message

integrity

AES-CCM, used for message integrity

Secure Simple Pairing: Protection

against passive eavesdropping

Elliptic Curve Diffie-Hellman

Exchange Ephemeral (ECDHE)

Elliptic Curve Diffie-Hellman Exchange

(ECDHE)

Secure Simple Pairing: Protection

against man-in-the-middle

(MITM) attacks

Two user-assisted numeric

methods: numerical comparison or

passkey entry

Two user-assisted numeric methods:

numerical comparison or passkey entry

Pairings require a user response,

including all non-MITM pairing modes

Bluetooth 4.1 or later i Mac Late 2015 or later

Mac Book Pro Early 2015 or later

iOS9 or later

iPadOS 13.1 or later

macOS 10.12 or later

tvOS9 or later

watchOS 2.0 or later

Bluetooth 4.2 or later i Phone 6 or later iOS9 or later

iPadOS 13.1 or later

macOS 10.12 or later

tvOS9 or later

watchOS 2.0 or later

173Apple Platform Security

Bluetooth Low Energy privacy

To help secure user privacy, BLE includes the following two features: address

randomisation and cross-transport key derivation.

Address randomisation is a feature that reduces the ability to track a BLE device over a

period of time by changing the Bluetooth device address on a frequent basis. For a device

using the privacy feature to reconnect to known devices, the device address, referred

to as the private address, must be resolvable by the other device. The private address

is generated using the device’s identity resolving key exchanged during the pairing

procedure.

iOS13 or later and iPadOS 13.1 or later have the ability to derive link keys across

transports, a feature known as cross-transport key derivation. For example, a link key

generated with BLE can be used to derive a Bluetooth Classic link key. In addition, Apple

added Bluetooth Classic to BLE support for devices that support the Secured Connections

feature that was introduced in the Bluetooth Core Specification 4.1 (see the Bluetooth Core

Specification 5.1).

Ultra Wideband security in iOS

The new Apple-designed U1 chip uses Ultra Wideband technology for spatial awareness —

allowing iPhone 11, iPhone 11 Pro and iPhone 11 Pro Max or later iPhone models to precisely

locate other U1-equipped Apple devices. Ultra Wideband technology uses the same

technology to randomise data found on other supported Apple devices:

• MAC address randomisation

• Wi-Fi frame sequence number randomisation

Single sign-on

Single sign-on security

Single sign-on

iOS and iPadOS support authentication to enterprise networks through Single sign-on

(SSO). SSO works with Kerberos-based networks to authenticate users to services they

are authorised to access. SSO can be used for a range of network activities, from secure

Safari sessions to third-party apps. Certificate-based authentication such as PKINIT is also

supported.

macOS supports authentication to enterprise networks using Kerberos. Apps can use

Kerberos to authenticate users to services they’re authorised to access. Kerberos can also

be used for a range of network activities, from secure Safari sessions and network file

system authentication to third-party apps. Certificate-based authentication is supported,

although app adoption of a developer API is required.

iOS, iPadOS and macOS SSO use SPNEGO tokens and the HTTP Negotiate protocol to work

with Kerberos-based authentication gateways and Windows Integrated Authentication systems

that support Kerberos tickets. SSO support is based on the open source Heimdal project.

174Apple Platform Security

The following encryption types are supported in iOS, iPadOS and macOS:

• AES-128-CTS-HMAC-SHA1-96

• AES-256-CTS-HMAC-SHA1-96

• DES3-CBC-SHA1

• ARCFOUR-HMAC-MD5

Safari supports SSO, and third-party apps that use standard iOS and iPadOS networking

APIs can also be configured to use it. To configure SSO, iOS and iPadOS support a

configuration profile payload that allows mobile device management (MDM) solutions to

push down the necessary settings. This includes setting the user principal name (that

is, the Active Directory user account) and Kerberos realm settings as well as configuring

which apps and Safari web URLs should be allowed to use SSO.

To configure Kerberos in macOS, acquire tickets with Ticket Viewer, log in to a Windows

Active Directory domain or use the kinit command-line tool.

Extensible Single sign-on

App developers can provide their own single sign-on implementations using SSO

extensions. SSO extensions are invoked when a native or web app needs to use some

identity provider for user authentication. Developers can provide two types of extensions:

those that redirect to HTTPS and those that use a challenge/response mechanism such as

Kerberos. This allows OpenID, OAuth, SAML2 and Kerberos authentication schemes to be

supported by Extensible Single sign-on.

To use a Single sign-on extension, an app can either use the AuthenticationServices API or

can rely on the URL interception mechanism offered by the operating system. WebKit and

CFNetwork provide an interception layer that permits seamless support of Single sign-on

for any native or WebKit app. For a Single sign-on extension to be invoked, a configuration

provided by an administrator has to be installed though a mobile device management

(MDM) profile. In addition, redirect type extensions must use the Associated Domains

payload to prove that the identity server they support is aware of their existence.

The only extension provided with the operating system is the Kerberos SSO extension.

AirDrop security

Apple devices that support AirDrop use Bluetooth Low Energy (BLE) and Apple-created

peer-to-peer Wi-Fi technology to send files and information to nearby devices, including

AirDrop-capable iOS devices and iPad devices with iOS7 or later and Mac computers

with OS X 10.11 or later. The Wi-Fi radio is used to communicate directly between devices

without using any internet connection or wireless access point (AP). This connection is

encrypted with TLS.

AirDrop is set to share with Contacts Only by default. Users can also choose to use AirDrop

to share with everyone, or turn off the feature entirely. Organisations can restrict the use of

AirDrop for devices or apps being managed by using a mobile device management (MDM)

solution.

175Apple Platform Security

AirDrop operation

AirDrop uses iCloud services to help users authenticate. When a user signs in to iCloud,

a 2048-bit RSA identity is stored on the device, and when the user turns on AirDrop, an

AirDrop short identity hash is created based on the email addresses and phone numbers

associated with the user’s AppleID.

When a user chooses AirDrop as the method for sharing an item, the sending device emits

an AirDrop signal over BLE that includes the user’s AirDrop short identity hash. Other Apple

devices that are awake, in close proximity and have AirDrop turned on detect the signal and

respond using peer-to-peer Wi-Fi so that the sending device can discover the identity of

any responding devices.

In Contacts Only mode, the received AirDrop short identity hash is compared with hashes

of people in the receiving device’s Contacts app. If a match is found, the receiving device

responds over peer-to-peer Wi-Fi with its identity information. If there is no match, the

device doesn’t respond.

In Everyone mode, the same overall process is used. However, the receiving device

responds even if there is no match in the device’s Contacts app.

The sending device then initiates an AirDrop connection using peer-to-peer Wi-Fi, using

this connection to send a long identity hash to the receiving device. If the long identity

hash matches the hash of a known person in the receiver’s Contacts, then the receiver

responds with its long identity hashes.

If the hashes are verified, the recipient’s first name and photo (if present in Contacts) are

displayed in the sender’s AirDrop share sheet. In iOS and iPadOS, they are shown in the

“People” or “Devices” section. Devices that aren’t verified or authenticated are displayed in

the sender’s AirDrop share sheet with a silhouette icon and the device’s name, as defined

in Settings > General > About > Name. In iOS and iPadOS, they are placed in the “Other

People” section of the AirDrop share sheet.

The sending user may then select who they want to share with. Upon user selection, the

sending device initiates an encrypted (TLS) connection with the receiving device, which

exchanges their iCloud identity certificates. The identity in the certificates is verified

against each user’s Contacts app.

If the certificates are verified, the receiving user is asked to accept the incoming transfer

from the identified user or device. If multiple recipients have been selected, this process is

repeated for each destination.

176Apple Platform Security

Wi-Fi password sharing security on iPhone

andiPad

iOS and iPadOS devices that support Wi-Fi password sharing use a mechanism similar to

AirDrop to send a Wi-Fi password from one device to another.

When a user selects a Wi-Fi network (requestor) and is prompted for the Wi-Fi password,

the Apple device starts a Bluetooth Low Energy (BLE) advertisement indicating that it

wants the Wi-Fi password. Other Apple devices that are awake, in close proximity and have

the password for the selected Wi-Fi network connect using BLE to the requesting device.

The device that has the Wi-Fi password (grantor) requires the Contact information of

the requestor, and the requestor must prove their identity using a similar mechanism to

AirDrop. After identity is proven, the grantor sends the requestor the passcode which can

be used to join the network.

Organisations can restrict the use of Wi-Fi password sharing for devices or apps being

managed through a mobile device management (MDM) solution.

Firewall security in macOS

macOS includes a built-in firewall to protect the Mac from network access and denial-of-

service attacks. It can be configured in the Security & Privacy pane of System Preferences

and supports the following configurations:

• Block all incoming connections, regardless of app.

• Automatically allow built-in software to receive incoming connections.

• Automatically allow downloaded and signed software to receive incoming connections.

• Add or deny access based on user-specified apps.

• Prevent the Mac from responding to ICMP (Internet Control Message Protocol) probing

and portscan requests.

177Apple Platform Security

Developer kit security

Developer kit security overview

Apple provides a number of “kit” frameworks to enable third-party developers to extend

Apple services. These frameworks are built with user privacy and security at their core:

• HomeKit

• CloudKit

• SiriKit

• DriverKit

• ReplayKit

• ARKit

HomeKit security

HomeKit communication security

HomeKit provides a home automation infrastructure that uses iCloud and iOS, iPadOS and

macOS security to protect and sync private data without exposing it to Apple.

HomeKit identity and security are based on Ed25519 public-private key pairs. An Ed25519

key pair is generated on the iOS, iPadOS and macOS device for each user for HomeKit,

which becomes their HomeKit identity. It’s used to authenticate communication between

iOS, iPadOS and macOS devices, and between iOS, iPadOS and macOS devices and

accessories.

The keys — stored in keychain and are included only in encrypted Keychain backups — are

kept up to date between devices using iCloud Keychain, where available. HomePod and

AppleTV receive keys using tap-to-set-up or the setup mode described below. Keys are

shared from an iPhone to a paired AppleWatch using AppleIDentity Service (IDS).

178Apple Platform Security

Communication between HomeKit accessories

HomeKit accessories generate their own Ed25519 key pair for use in communicating with

iOS, iPadOS and macOS devices. If the accessory is restored to factory settings, a new key

pair is generated.

To establish a relationship between an iOS, iPadOS and macOS device and a HomeKit

accessory, keys are exchanged using Secure Remote Password (3072-bit) protocol

utilising an eight-digit code provided by the accessory’s manufacturer, entered on the iOS

or iPadOS device by the user, and then encrypted using ChaCha20-Poly1305 AEAD with

HKDF-SHA512 derived keys. The accessory’s MFi certification is also verified during setup.

Accessories without an MFi chip can build in support for software authentication in iOS 11.3

or later.

When the iOS, iPadOS and macOS device and the HomeKit accessory communicate during

use, each authenticates the other using the keys exchanged in the above process. Each

session is established using the Station-to-Station protocol and is encrypted with HKDF-

SHA512 derived keys based on per-session Curve25519 keys. This applies to both IP-

based and Bluetooth Low Energy (BLE) accessories.

For BLE devices that support broadcast notifications, the accessory is provisioned with

a broadcast encryption key by a paired iOS, iPadOS and macOS device over a secure

session. This key is used to encrypt the data about state changes on the accessory, which

are notified using the BLE advertisements. The broadcast encryption key is an HKDF-

SHA512 derived key, and the data is encrypted using ChaCha20-Poly1305 AEAD algorithm.

The broadcast encryption key is periodically changed by the iOS, iPadOS and macOS

device and updated to other devices using iCloud as described in HomeKit data security.

HomeKit and Siri

Siri can be used to query and control accessories and to activate scenes. Minimal

information about the configuration of the home is provided anonymously to Siri, to provide

names of rooms, accessories and scenes that are necessary for command recognition.

Audio sent to Siri may denote specific accessories or commands but such Siri data isn’t

associated with other Apple features such as HomeKit.

Siri-enabled HomeKit accessories

Users can enable new features like Siri, and other HomePod features like timers, alarms,

intercom and doorbell, on Siri-enabled accessories using the Home app. When these

features are enabled, the accessory coordinates with a paired HomePod on the local

network that hosts these Apple features. Audio is exchanged between the devices over

encrypted channels using both HomeKit and AirPlay protocols.

When Listen for Hey Siri is turned on, the accessory listens for the “Hey Siri” phrase using

a locally running trigger-phrase detection engine. If this engine detects the phrase, it

sends the audio frames directly to a paired HomePod using HomeKit. The HomePod does a

second check on the audio and may cancel the audio session if the phrase doesn’t appear

to contain the trigger phrase.

When Touch for Siri is turned on, the user can press a dedicated button on the accessory

to start a conversation with Siri. The audio frames are sent directly to the paired HomePod.

179Apple Platform Security

After a successful invocation of Siri is detected, the HomePod sends the audio to Siri

servers and fulfils the user’s intent using the same security, privacy and encryption

safeguards that the HomePod applies to user invocations made to the HomePod itself. If

Siri has an audio reply, then Siri’s response is sent over an AirPlay audio channel to the

accessory. Some Siri requests require additional information from the user (for example,

asking if they want to hear more options). In that case, the accessory receives an indication

that the user should be prompted, and the additional audio is streamed to the HomePod.

The accessory is required to have a visual indicator to signal to a user when it’s actively

listening (for example, an LED indicator). The accessory has no knowledge of the intent of

the Siri request, except for access to the audio streams, and no user data is stored on the

accessory.

HomeKit data security

HomeKit data can be securely updated between a user’s iOS, iPadOS and macOS devices

using iCloud and iCloud keychain. During this process, the HomeKit data is encrypted

using keys derived from the user’s HomeKit identity and a random nonce and is handled

as an opaque binary large object, or blob. The most recent blob is stored in iCloud but

it isn’t used for any other purpose. Because it’s encrypted using keys that are available

only on the user’s iOS, iPadOS and macOS devices, its contents are inaccessible during

transmission and iCloud storage.

HomeKit data is also synced between multiple users of the same home. This process uses

authentication and encryption that is the same as that used between an iOS, iPadOS and

macOS device and a HomeKit accessory. The authentication is based on Ed25519 public

keys that are exchanged between the devices when a user is added to a home. After a new

user is added to a home, all further communication is authenticated and encrypted using

Station-to-Station protocol and per-session keys.

The user who initially created the home in HomeKit or another user with editing

permissions can add new users. The owner’s device configures the accessories with the

public key of the new user so that the accessory can authenticate and accept commands

from the new user. When a user with editing permissions adds a new user, the process is

delegated to a home hub to complete the operation.

HomeKit and AppleTV

The process to provision AppleTV for use with HomeKit is performed automatically when

the user signs in to iCloud. The iCloud account needs to have two-factor authentication

enabled. AppleTV and the owner’s device exchange temporary Ed25519 public keys

over iCloud. When the owner’s device and AppleTV are on the same local network, the

temporary keys are used to secure a connection over the local network using Station-to-

Station protocol and per-session keys. This process uses authentication and encryption

that is the same as that used between an iOS, iPadOS and macOS device and a HomeKit

accessory. Over this secure local connection, the owner’s device transfers the user’s

Ed25519 public-private key pairs to AppleTV. These keys are then used to secure the

communication between AppleTV and the HomeKit accessories and also between

AppleTV and other iOS, iPadOS and macOS devices that are part of the HomeKit home.

If a user doesn’t have multiple devices and doesn’t grant additional users access to their

home, no HomeKit data is transmitted to iCloud.

180Apple Platform Security

Home data and apps

Access to home data by apps is controlled by the user’s Privacy settings. Users are asked

to grant access when apps request home data, similar to Contacts, Photos and other iOS,

iPadOS and macOS data sources. If the user approves, apps have access to the names of

rooms, names of accessories, which room each accessory is in and other information as

detailed in the HomeKit developer documentation at https://developer.apple.com/homekit/.

Local data storage

HomeKit stores data about the homes, accessories, scenes and users on a user’s iOS,

iPadOS and macOS devices. This stored data is encrypted using keys derived from the

user’s HomeKit identity keys, plus a random nonce. Additionally, HomeKit data is stored

using the Data Protection class Protected Until First User Authentication. HomeKit data

is backed up only in encrypted backups, so, for example, unencrypted backups to the

Finder (macOS 10.15 or later) or iTunes (macOS 10.14 or earlier) through USB don’t contain

HomeKit data.

Securing routers with HomeKit

Routers that support HomeKit let users improve the security of their home network by

managing the Wi-Fi access that HomeKit accessories have to their local network and to

the internet. The routers also support Private PSK (PPSK) authentication, so accessories

can be added to the Wi-Fi network using a key that’s specific to the accessory, which can

be revoked when needed. PPSK authentication improves security by not exposing the main

Wi-Fi password to accessories, as well as by allowing the router to securely identify an

accessory even if it were to change its MAC address.

Using the Home app, a user can configure access restrictions for groups of accessories as

follows:

• No restriction: Allow unrestricted access to the internet and the local network.

• Automatic: This is the default setting. Allow access to the internet and the local network

based on a list of internet sites and local ports provided to Apple by the accessory

manufacturer. This list includes all sites and ports needed by the accessory to function

properly. (No Restriction is in place until such a list is available.)

• Restrict to Home: No access to the internet or the local network except for the

connections required by HomeKit to discover and control the accessory from the local

network (including from the home hub to support remote control).

A PPSK is a strong, accessory-specific WPA2 Personal pass-phrase that is automatically

generated by HomeKit and revoked if and when the accessory is later removed from the

Home. A PPSK is used when an accessory is added to the Wi-Fi network by HomeKit in a

Home that has been configured with a HomeKit router; this addition is reflected as Wi-

Fi Credential: HomeKit-managed on the settings screen for the accessory in the Home

app. Accessories that were added to the Wi-Fi network before adding the router are

reconfigured to use a PPSK if the accessory supports this; otherwise, they retain their

existing credentials.

As an additional security measure, users must configure the HomeKit router using the

router manufacturer’s app, so that the app can validate that users have access to the

router and can add it to the Home app.

181Apple Platform Security

HomeKit camera security

Cameras that have an Internet Protocol address (IP address) in HomeKit send video and

audio streams directly to the iOS, iPadOS, tvOS and macOS device on the local network

accessing the stream. The streams are encrypted using randomly generated keys on the

device and an Internet Protocol camera (or IP camera), and they’re exchanged over the

secure HomeKit session to the camera. When a device isn’t on the local network, the

encrypted streams are relayed through the home hub to the device. The home hub doesn’t

decrypt the streams; it functions only as a relay between the device and the IP camera.

When an app displays the HomeKit IP camera video view to the user, HomeKit renders the

video frames securely from a separate system process. As a result, the app is unable to

access or store the video stream. In addition, apps aren’t permitted to capture screenshots

from this stream.

HomeKit secure video

HomeKit provides an end-to-end secure and private mechanism to record, analyse and

view clips from HomeKit IP cameras without exposing that video content to Apple or any

third party. When motion is detected by the IP camera, video clips are sent directly to an

Apple device acting as a home hub, using a dedicated local network connection between

that home hub and the IP camera. The local network connection is encrypted with a

per-session HKDF-SHA512 derived key-pair that is negotiated over the HomeKit session

between home hub and IP camera. HomeKit decrypts the audio and video streams on the

home hub and analyses the video frames locally for any significant event. If a significant

event is detected, HomeKit encrypts the video clip using AES-256-GCM with a randomly

generated AES256 key. HomeKit also generates poster frames for each clip and these

poster frames are encrypted using the same AES256 key. The encrypted poster frame and

audio and video data are uploaded to iCloud servers. The related metadata for each clip

including the encryption key are uploaded to CloudKit using iCloud end-to-end encryption.

For face classification, HomeKit stores all data used to classify a particular person’s face in

CloudKit using iCloud end-to-end encryption. The data stored includes information about

each person, such as name, as well as images representing that person’s face. These face

images can be sourced from a user’s Photos if they opt in, or they can be collected from

previously analysed IP camera video. A HomeKit Secure Video analysis session uses this

classification data to identify faces in the secure video stream it receives directly from

the IP camera and includes that identification information in the clip metadata mentioned

previously.

When the Home app is used to view the clips of a camera, the data is downloaded from

iCloud and the keys to decrypt the streams are unwrapped locally using iCloud end-to-

end decryption. The encrypted video content is streamed from the servers and decrypted

locally on the iOS device before displaying it in the viewer. Each video clip session may be

broken down into subsections, with each subsection encrypting the content stream with its

own unique key.

182Apple Platform Security

HomeKit security with AppleTV

HomeKit securely connects some third-party remote accessories to AppleTV and supports

adding user profiles to the owner of the home’s AppleTV.

Using third-party remote accessories with AppleTV

Some third-party remote accessories provide Human Interface Design (HID) events and

Siri audio to an associated AppleTV added using the Home app. The remote sends the

HID events over the secure session to the AppleTV. A Siri-capable TV remote sends audio

data to AppleTV when the user explicitly activates the microphone on the remote using a

dedicated Siri button. The remote sends the audio frames directly to the AppleTV using

a dedicated local network connection. A per-session HKDF-SHA512 derived key-pair that

is negotiated over the HomeKit session between AppleTV and the TV remote is used to

encrypt the local network connection. HomeKit decrypts the audio frames on AppleTV and

forwards them to the Siri app, where they are treated with the same privacy protections as

all Siri audio input.

AppleTV profiles for HomeKit homes

When a user of a HomeKit home adds their profile to the owner of the home’s AppleTV,

it gives that user access to their TV shows, music and podcasts. Settings for each user

regarding their profile use on the AppleTV are shared to the owner’s iCloud account using

iCloud end-to-end encryption. The data is owned by each user and is shared as read-only

to the owner. Each user of the home can change these values in the Home app and the

AppleTV of the owner uses these settings.

When a setting is turned on, the iTunes account of the user is made available on the

AppleTV. When a setting is turned off, all account and data pertaining to that user is

deleted on the AppleTV. The initial CloudKit share is initiated by the user’s device and the

token to establish the secure CloudKit share is sent over the same secure channel that is

used to sync data between users of the home.

SiriKit security for iOS, iPadOS and watchOS

Siri uses the app extension system to communicate with third-party apps. On a device,

Siri can access the user’s contact information and the device’s current location. But

before it provides protected data to an app, Siri checks the app’s user-controlled access

permissions. According to those permissions, Siri passes only the relevant fragment of the

original user utterance to the app extension. For example, if an app doesn’t have access

to contact information, Siri won’t resolve a relationship in a user request such as “Pay my

mother 10 pounds using Payment App”. In this case, the app would see only the literal term

“my mother”.

However, if the user has granted the app access to contact information, the app would

receive resolved information about the user’s mother. If a relationship is referenced in the

body portion of a message — for example, “Tell my mother on MessageApp that my brother

is awesome” — Siri doesn’t resolve “my brother” regardless of the app’s permissions.

183Apple Platform Security

SiriKit-enabled apps can send app-specific or user-specific vocabulary to Siri, such as the

names of the user’s contacts. This information allows Siri’s speech recognition and natural

language understanding to recognise vocabulary for that app, and is associated with a

random identifier. The custom information remains available as long as the identifier is in

use, until the user disables the app’s Siri integration in Settings or until the SiriKit-enabled

app is uninstalled.

For an utterance like “Get me a ride to my mum’s home using RideShareApp”, the request

requires location data from the user’s contacts. For that request only, Siri provides the

required information to the app’s extension regardless of the user permission settings for

location or contact information for the app.

DriverKit security for macOS

DriverKit is the framework that allows developers to create device drivers that the user

installs on their Mac. Drivers built with DriverKit run in user space, rather than as kernel

extensions, for improved system security and stability. This makes for easier installation

and increases the stability and security of macOS.

The user simply downloads the app (installers aren’t necessary when using system

extensions or DriverKit) and the extension is enabled only when required. These replace

kexts for many use cases, which require administrator privileges to install in /System/

Library or /Library.

IT administrators who use device drivers, cloud storage solutions, networking, and security

apps that require kernel extensions are encouraged to move to newer versions that are

built on system extensions. These newer versions greatly reduce the possibility of kernel

panics on the Mac as well as reduce the attack surface. These new extensions run in the

user space, won’t require special privileges required for installation and are automatically

removed when the bundling app is moved to the Bin.

The DriverKit framework provides C++ classes for I/O services, device matching, memory

descriptors and dispatch queues. It also defines I/O-appropriate types for numbers,

collections, strings and other common types. The user uses these with family-specific

driver frameworks like USBDriverKit and HIDDriverKit. Use the System Extensions

framework to install and upgrade a driver.

ReplayKit security in iOS and iPadOS

ReplayKit is a framework that allows developers to add recording and live broadcasting

capabilities to their apps. In addition, it allows users to annotate their recordings and

broadcasts using the device’s front-facing camera and microphone.

184Apple Platform Security

Movie recording

There are several layers of security built into recording a movie:

• Permissions dialogue: Before recording starts, ReplayKit presents a user consent alert

requesting that the user acknowledge their intent to record the screen, the microphone

and the front-facing camera. This alert is presented once per app process and it’s

presented again if the app is left in the background for longer than 8 minutes.

• Screen and audio capture: Screen and audio capture occurs out of the app’s process in

the ReplayKit daemon replayd. This is designed to ensure the recorded content is never

accessible to the app process.

• In-app screen and audio capture: This allows an app to get video and sample buffers,

which are guarded by the permissions dialogue.

• Movie creation and storage: The movie file is written to a directory that’s only

accessible to the ReplayKit subsystems and is never accessible to any apps. This helps

prevent recordings being used by third parties without the user’s consent.

• End-user preview and sharing: The user has the ability to preview and share the movie

with a user interface vended by ReplayKit. The user interface is presented out-of-

process through the iOS Extension infrastructure and has access to the generated

movie file.

ReplayKit broadcasting

There are several layers of security built into broadcasting a video:

• Screen and audio capture: The screen and audio capture mechanism during

broadcasting is identical to movie recording and occurs in replayd.

• Broadcast extensions: For third-party services to participate in ReplayKit broadcasting,

they’re required to create two new extensions that are configured with the com.apple.

broadcast-services endpoint:

• A user interface extension that allows the user to set up their broadcast

• An upload extension that handles uploading video and audio data to the service’s

back-end servers

The architecture helps ensure that hosting apps have no privileges to the broadcasted video

and audio contents. Only ReplayKit and the third-party broadcast extensions have access.

• Broadcast picker: With the broadcast picker, users initiate system broadcasts directly

from their app using the same system-defined user interface that’s accessible using

Control Centre. The user interface is implemented using a private API and is an

extension that lives within the ReplayKit framework. It is out-of-process from the

hosting app.

• Upload extension: The extension that third-party broadcast services implement to

handle video and audio content during broadcasting uses raw unencoded sample

buffers. During this mode of handling, video and audio data is serialised and passed to

the third-party upload extension in real time through a direct XPC connection. Video

data is encoded by extracting the IOSurface object from the video sample buffer,

encoding it securely as an XPC object, sending it over through XPC to the third-party

extension and decoding it securely back into an IOSurface object.

185Apple Platform Security

ARKit security in iOS and iPadOS

ARKit is a framework that lets developers produce augmented reality experiences in their

app or game. Developers can add 2D or 3D elements using the front or rear camera of an

iOS or iPadOS device.

Apple designed cameras with privacy in mind and third-party apps must obtain the user’s

consent before accessing the camera. In iOS and iPadOS, when a user grants an app

access to their camera, that app can access real-time images from the front and rear

cameras. Apps aren’t allowed to use the camera without transparency that the camera is

in use.

Photos and videos taken with the camera may contain other information, such as where

and when they were taken, the depth of field and overcapture. If users don’t want photos

and videos taken with the Camera app to include location, they can control this at any time

by going to Settings > Privacy > Location Services > Camera. If users don’t want photos

and video to include location when shared, they can turn location off in the Options menu

in the share sheet.

To better position the user’s AR experience, apps that use ARKit can use world- or face-

tracking information from the other camera. World tracking uses algorithms on the user’s

device to process information from these sensors to determine their position relative to a

physical space. World tracking enables features such as Optical Heading in Maps.

186Apple Platform Security

Secure device management

Secure device management overview

iOS, iPadOS, macOS and tvOS support flexible security policies and configurations that

are easy to enforce and manage. Through them, organisations can protect corporate

information and help ensure that employees meet enterprise requirements, even if they

are using devices they’ve provided themselves — for example, as part of a “bring your own

device” (BYOD) programme.

Organisations can use resources such as password protection, configuration profiles,

remote wipe and third-party mobile device management (MDM) solutions to manage fleets

of devices and help keep corporate data secure even when employees access this data on

their personal devices.

In iOS13 or later, iPadOS 13.1 or later, and macOS 10.15 or later, Apple devices support a

new user enrolment option specifically designed for BYOD programmes. User enrolments

provide more autonomy for users on their own devices, while increasing the security of

enterprise data by storing it on a separate, cryptographically protected APFS (Apple File

System) volume. This provides a better balance of security, privacy and user experience for

BYOD programmes.

Pairing model security for iPhone and iPad

iOS and iPadOS use a pairing model to control access to a device from a host computer.

Pairing establishes a trust relationship between the device and its connected host,

signified by public key exchange. iOS and iPadOS also use this sign of trust to enable

additional functionality with the connected host, such as data syncing. In iOS9 or later,

services:

• That require pairing can’t be started until after the device has been unlocked by the user

• Won’t start unless the device has been recently unlocked

• May require the device to be unlocked to begin (such as with photo syncing)

187Apple Platform Security

The pairing process requires the user to unlock the device and accept the pairing request

from the host. In iOS9 or later, the user is also required to enter their passcode, after

which the host and device exchange and save 2048-bit RSA public keys. The host is then

given a 256-bit key that can unlock an escrow keybag stored on the device. The exchanged

keys are used to start an encrypted SSL session, which the device requires before it sends

protected data to the host or starts a service (iTunes or Finder syncing, file transfers,

Xcode development and so on). To use this encrypted session for all communication, the

device requires connections from a host over Wi-Fi, so it must have been previously paired

over USB. Pairing also enables several diagnostic capabilities. In iOS 9, if a pairing record

hasn’t been used for more than 6 months, it expires. In iOS11 or later, this time frame is

shortened to 30 days.

Certain diagnostic services, including com.apple.mobile.pcapd, are restricted to work

only over USB. Additionally, the com.apple.file_relay service requires an Apple-signed

configuration profile to be installed. In iOS11 or later, AppleTV can use the Secure Remote

Password protocol to wirelessly establish a pairing relationship.

A user can clear the list of trusted hosts with the Reset Network Settings or Reset Location

& Privacy options.

Mobile device management

Mobile device management security overview

Apple operating systems support mobile device management (MDM), which allows

organisations to securely configure and manage scaled Apple device deployments.

How MDM works securely

MDM capabilities are built on existing operating system technologies, such as configuration

profiles, over-the-air enrolment and the Apple Push Notification service (APNs). For

example, APNs is used to wake the device so it can communicate directly with its MDM

solution over a secured connection. With APNs, no confidential or proprietary information

is transmitted.

Using MDM, IT departments can enrol Apple devices in an enterprise environment,

wirelessly configure and update settings, monitor compliance with corporate policies,

manage software update policies and even remotely wipe or lock managed devices.

In addition to the traditional device enrolments supported by iOS, iPadOS, macOS and

tvOS, an enrolment type has been added in iOS13 or later, iPadOS 13.1 or later, and

macOS 10.15 or later — User Enrolment. User enrolments are MDM enrolments specifically

targeting “bring your own device” (BYOD) deployments where the device is personally

owned but used in a managed environment. User enrolments grant the MDM solution more

limited privileges than unsupervised device enrolments do and provide cryptographic

separation of user and corporate data.

188Apple Platform Security

Enrolment types

• Automated Device Enrolment: Automated Device Enrolment lets organisations configure

and manage devices from the moment the devices are removed from the box (in a

process known as Auto Advance deployment). These devices are known as supervised,

and users have the option to prevent the MDM profile from being removed by the user.

Automated Device Enrolment is designed for devices owned by the organisation.

• Device Enrolment: Device Enrolment allows organisations to have users manually enrol

devices and then manage many different aspects of device use, including the ability to

erase the device. Device Enrolment also has a larger set of payloads and restrictions

that can be applied to the device. When a user removes an enrolment profile, all

configuration profiles, their settings and managed apps based on that enrolment profile

are removed with it.

• User Enrolment: User Enrolment is designed for devices owned by the user and

is integrated with Managed AppleIDs to establish a user identity on the device.

Managed AppleIDs are part of the User Enrolment profile, and the user must

successfully authenticate in order for enrolment to be completed. Managed AppleIDs

can be used alongside a personal AppleID that the user has already signed in with.

Managed apps and accounts use a Managed AppleID, and personal apps and accounts

use a personal AppleID.

Device restrictions

Restrictions can be enabled — or in some cases, disabled — by administrators to help

prevent users from accessing a specific app, service or function of an iPhone, iPad,

Mac or AppleTV that’s enrolled in an MDM solution. Restrictions are sent to devices in

a restrictions payload which is part of a configuration profile. Certain restrictions on an

iPhone may be mirrored on a paired AppleWatch.

Passcode and password settings management

By default, the user’s passcode can be defined as a numeric PIN. In iOS and iPadOS

devices with FaceID or TouchID, the minimum passcode length is four digits. Because

longer and more complex passcodes are harder to guess or attack, they are recommended.

Administrators can enforce complex passcode requirements and other policies using MDM

or Microsoft Exchange ActiveSync, or by requiring users to manually install configuration

profiles. An administrator password is needed for the macOS passcode policy payload

installation. Some passcode policies can require a certain passcode length, composition or

other attributes.

189Apple Platform Security

Configuration profile enforcement

Configuration profiles are the primary way that an MDM solution delivers and manages

policies and restrictions on managed devices. If organisations need to configure a large

number of devices — or to provide lots of custom email settings, network settings or

certificates to a large number of devices — configuration profiles are a safe and secure way

to do it.

Configuration profiles

A configuration profile is an XML file (ending in .mobileconfig) that consists of payloads

that load settings and authorisation information onto Apple devices. Configuration profiles

automate the configuration of settings, accounts, restrictions and credentials. These files

can be created by an MDM solution or Apple Configurator for Mac, or they can be created

manually. Before organisations send a configuration profile to an Apple device, they must

enrol the device in the MDM solution using an enrolment profile.

Enrolment profiles

An enrolment profile is a configuration profile with an MDM payload that enrols the device

in the MDM solution specified for that device. This allows the MDM solution to send

commands and configuration profiles to the device and to query certain aspects of the

device. When a user removes an enrolment profile, all configuration profiles, their settings

and managed apps based on that enrolment profile are removed with it. There can be only

one enrolment profile on a device at a time.

Configuration profile settings

A configuration profile contains a number of settings in specific payloads that can be

specified, including (but not limited to):

• Passcode and password policies

• Restrictions on device features (for example, disabling the camera)

• Network and VPN settings

• Microsoft Exchange settings

• Mail settings

• Account settings

• LDAP directory service settings

• CalDAV calendar service settings

• Credentials and keys

• Software updates

190Apple Platform Security

Profile signing and encryption

Configuration profiles can be signed to validate their origin, and encrypted to help ensure

their integrity and protect their contents. Configuration profiles for iOS and iPadOS

are encrypted using the Cryptographic Message Syntax (CMS) specified in RFC 5652,

supporting 3DES and AES128.

Profile installation

Users can install configuration profiles directly on their devices using Apple Configurator

for Mac, or they can be downloaded using Safari, sent attached to a mail message,

transferred using AirDrop or the Files app in iOS and iPadOS, or sent over the air using

a mobile device management (MDM) solution. When a user sets up a device in Apple

School Manager or Apple Business Manager, the device downloads and installs a profile

for MDM enrolment. For information on how to remove profiles, see Intro to mobile device

management in Apple Platform Deployment.

Note: On supervised devices, configuration profiles can also be locked to a device. This

is designed to prevent their removal or to allow removal only with a passcode. Because

many organisations own their iOS and iPadOS devices, configuration profiles that bind

a device to an MDM solution can be removed — but doing so also removes all managed

configuration information, data and apps.

Automated Device Enrolment

Organisations can automatically enrol iOS, iPadOS, macOS and tvOS devices in mobile

device management (MDM) without having to physically touch or prepare the devices

before users get them. After enrolling in one of the services, administrators sign in to the

service website and link the programme to their MDM solution. The devices they purchased

can then be assigned to users through MDM. During the device configuration process, the

security of sensitive data can be increased by ensuring appropriate security measures are

in place. For example:

• Have users authenticate as part of the initial setup flow in the Apple device’s Setup

Assistant during activation.

• Provide a preliminary configuration with limited access and require additional device

configuration to access sensitive data.

After a user has been assigned, any MDM-specified configurations, restrictions or controls

are automatically installed. All communications between devices and Apple servers are

encrypted in transit through HTTPS (TLS).

The setup process for users can be further simplified by removing specific steps in the

Setup Assistant for devices so that users are up and running quickly. Administrators can

also control whether users can remove the MDM profile from the device and help ensure

that device restrictions are in place throughout the life cycle of the device. Once the

device is unboxed and activated, it can enrol in the organisation’s MDM solution — and all

management settings, apps and books are installed as defined by the MDM administrator.

191Apple Platform Security

Apple School Manager, Apple Business Manager and Apple Business

Essentials

Apple School Manager, Apple Business Manager and Apple Business Essentials are

services for IT administrators to deploy Apple devices that an organisation has purchased

directly from Apple or through participating Apple Authorised Resellers and network

providers.

When used with an MDM solution, administrators can simplify the setup process for

users, configure device settings, and distribute apps and books purchased in these three

services. Apple School Manager also integrates with Student Information Systems (SISs)

directly or using SFTP, and all three services can use System for Cross-domain Identity

Management (SCIM) or federated authentication with Microsoft Azure Active Directory

(Azure AD) so administrators can quickly create accounts.

Apple maintains certifications in compliance with the ISO/IEC 27001 and 27018 standards

to enable Apple customers to address their regulatory and contractual obligations.

These certifications provide our customers with an independent attestation over Apple’s

Information Privacy and Security practices for in-scope systems. For more information, see

Apple internet services security certifications in Apple Platform Certifications.

Note: To learn whether an Apple programme is available in a specific country or region,

see the Apple Support article Availability of Apple programmes and payment methods for

education and business.

Device supervision

Supervision generally denotes that the device is owned by the organisation, giving them

additional control over the device’s configuration and restrictions. For more information,

see About Apple device supervision in Apple Platform Deployment.

Activation Lock security

How Apple enforces Activation Lock varies depending on whether the device is an iPhone

or an iPad, a Mac with Apple silicon or an Intel-based Mac with the Apple T2 Security Chip.

Behaviour on iPhone and iPad

On iPhone and iPad devices, Activation Lock is enforced through the activation process

after the Wi-Fi selection screen in iOS and iPadOS Setup Assistant. When a device

indicates its activating, it sends a request to an Apple server to get an activation

certificate. Devices that are Activation Locked prompt the user for the iCloud credentials

of the user that enabled Activation Lock at this time. iOS and iPadOS Setup Assistant won’t

progress unless a valid certificate can be obtained.

192Apple Platform Security

Behaviour on a Mac with Apple silicon

In a Mac with Apple silicon, LLB verifies that a valid LocalPolicy for the device exists and

that the LocalPolicy policy nonce values match the values stored in the Secure Storage

Component. LLB boots to recoveryOS if:

• There is no LocalPolicy for the current macOS

• The LocalPolicy is invalid for that macOS

• The LocalPolicy nonce hash values don’t match the hashes of values stored in the

Secure Storage Component

recoveryOS detects that the Mac computer isn’t activated and contacts the activation

server to get an activation certificate. If the device is Activation Locked, recoveryOS

prompts the user for iCloud credentials of the user that enabled Activation Lock at this

time. After a valid activation certificate is obtained, that activation certificate key is used

to obtain a RemotePolicy certificate. The Mac computer uses the LocalPolicy key and

RemotePolicy certificate to produce a valid LocalPolicy. LLB won’t allow booting of macOS

unless a valid LocalPolicy is present.

Behaviour on Intel-based Mac computers

In an Intel-based Mac with a T2 chip, the T2 chip firmware verifies that a valid activation

certificate is present before allowing the computer to boot to macOS. UEFI firmware loaded

by the T2 chip is responsible for querying the activation status of the device from the T2

chip and booting to recoveryOS instead of booting to macOS if a valid activation certificate

isn’t present. recoveryOS detects that the Mac isn’t activated and contacts the activation

server to get an activation certificate. If the device is Activation Locked, recoveryOS

prompts the user for iCloud credentials of the user that enabled Activation Lock at this

time. UEFI firmware won’t allow booting of macOS unless a valid activation certificate is

present.

Managed Lost Mode and remote wipe

Managed Lost Mode is used to locate supervised devices when they are stolen. After they

are located, they can be remotely locked or erased.

Managed Lost Mode

If a supervised iOS or iPadOS device with iOS9 or later is lost or stolen, a mobile device

management (MDM) administrator can remotely enable Lost Mode (called Managed Lost

Mode) on that device. When Managed Lost Mode is enabled, the current user is logged out

and the device can’t be unlocked. The screen displays a message that can be customised

by the administrator, such as displaying a phone number to call if the device is found. The

administrator can also request the device to send its current location (even if Location

Services are off) and, optionally, play a sound. When an administrator turns off Managed

Lost Mode, which is the only way the mode can be exited, the user is informed of this

action through a message on the Lock Screen or an alert on the Home Screen.

193Apple Platform Security

Remote wipe

iOS, iPadOS and macOS devices can be erased remotely by an administrator or user

(instant remote wipe is available only if the Mac has FileVault enabled). Instant remote

wipe is achieved by securely discarding the media key from Effaceable Storage, rendering

all data unreadable. For remote wipe through Microsoft Exchange ActiveSync, the device

checks in with the Microsoft Exchange Server before performing the wipe.

When a remote wipe command is triggered by MDM or iCloud, the iPhone, iPad, iPodtouch

or Mac device sends an acknowledgement back to the MDM solution and performs

the wipe.

Remote wipe isn’t possible in the following situations:

• With User Enrolment

• Using Microsoft Exchange ActiveSync when the account that was installed with User

Enrolment

• Using Microsoft Exchange ActiveSync if the device is supervised

Users can also wipe iOS and iPadOS devices in their possession using the Settings app.

And as mentioned, iOS and iPadOS devices can be set to automatically wipe after a series

of failed passcode attempts.

Shared iPad security in iPadOS

Shared iPad is a multi-user mode for use in iPad deployments. It allows users to share an

iPad while maintaining separation of documents and data for each user. Each user gets

their own private, reserved storage location, which is implemented as an APFS (Apple

File System) volume protected by the user’s credential. Shared iPad requires the use of a

Managed AppleID that’s issued and owned by the organisation.

With Shared iPad, a user can sign in to any organisationally owned device that is

configured for use by multiple users. User data is partitioned into separate directories,

each in their own data protection domains and protected by both UNIX permissions and

sandboxing. In iPadOS 13.4 or later, users can also sign in to a temporary session. When

the user signs out of a temporary session, their APFS volume is deleted and its reserved

space is returned to the system.

Signing in to Shared iPad

Both native and federated Managed AppleIDs are supported when signing in to

Shared iPad. When using a federated account for the first time, the user is redirected to

the Identity Provider’s (IdP) sign-in portal. Once authenticated, a short-lived access token

is issued for the backing Managed AppleIDs — and the login process proceeds similarly

to the native Managed AppleIDs sign-in process. Once signed in, Setup Assistant on

Shared iPad prompts the user to establish a passcode (credential) used to secure the local

data on the device and to authenticate to the login screen in the future. Like a single-

user device, in which the user would sign in once to their Managed AppleID using their

federated account and then unlock their device with their passcode, on Shared iPad, the

user signs in once using their federated account and from then on uses their established

passcode.

194Apple Platform Security

When a user signs in without federated authentication, the Managed AppleID is

authenticated with AppleIDentity Service (IDS) using the SRP protocol. If authentication

is successful, a short-lived access token specific to the device is granted. If the user has

used the device before, they already have a local user account, which is unlocked using the

same credential.

If the user hasn’t used the device before or is using the temporary session feature,

Shared iPad provisions a new UNIX user ID, an APFS volume to store the user’s personal

data and a local keychain. As storage is allocated (reserved) for the user at the time the

APFS volume is created, there may be insufficient space to create a new volume. In such an

event, the system identifies an existing user whose data has finished syncing to the cloud

and evicts that user from the device so the new user can sign in. In the unlikely event that

all existing users haven’t completed uploading their cloud data, the new user sign-in fails.

To sign in, the new user will need to wait for one user’s data to finish syncing or ask an

administrator to forcibly delete an existing user account, thereby risking data loss.

If the device isn’t connected to the internet (for example, if the user has no Wi-Fi access

point), authentication can occur against the local account for a limited number of days. In

that situation, only users with previously existing local accounts or a temporary session can

local account already exists.

After a user’s local account has been unlocked or created, if it’s remotely authenticated,

the short-lived token issued by Apple’s servers is converted to an iCloud token that permits

sign-in to iCloud. Next, the users’ settings are restored and their documents and data are

synced from iCloud.

While a user session is active and the device remains online, documents and data are

stored on iCloud as they are created or modified. In addition, a background syncing

mechanism helps ensure that changes are pushed to iCloud, or to other web services using

NSURLSession background sessions, after the user signs out. After background syncing for

that user is complete, the user’s APFS volume is unmounted and can’t be mounted again

without the user signing back in.

Temporary sessions don’t sync data with iCloud, and although a temporary session can

continue syncing data when the temporary session ends.

Signing out of Shared iPad

When a user signs out of Shared iPad, that user’s keybag is immediately locked and all

apps are shut down. To accelerate the case of a new user signing in, iPadOS defers some

ordinary sign-out actions temporarily and presents a login window to the new user. If a user

signs in during this time (approximately 30 seconds), Shared iPad performs the deferred

cleanup as part of signing in to the new user account. However, if Shared iPad remains idle

it triggers the deferred cleanup. During the cleanup phase, Login Window is restarted as if

another sign-out had occurred.

When a temporary session ends, Shared iPad performs the full logout sequence and

deletes the temporary session’s APFS volume immediately.

195Apple Platform Security

Apple Configurator security

Apple Configurator for Mac features a flexible, secure, device-centric design that lets an

administrator quickly and easily configure one or dozens of iOS, iPadOS and tvOS devices

connected to a Mac through USB (or tvOS devices paired through Bonjour) before giving

them to users. With Apple Configurator for Mac, an administrator can update software,

install apps and configuration profiles, rename and change wallpaper on devices, export

device information and documents, and much more.

Apple Configurator for Mac can also revive or restore Mac computers with Apple silicon

and those with the Apple T2 Security Chip. When a Mac is revived or restored in this

manner, the file containing the latest minor updates to the operating systems (macOS,

recoveryOS for Apple silicon or sepOS for T2) is securely downloaded from Apple servers

and installed directly on the Mac. After a successful revive or restore, the file is deleted

from the Mac using Apple Configurator. At no time can the user inspect or use this file

outside Apple Configurator.

Administrators can also choose to add devices to Apple School Manager, Apple

Business Manager or Apple Business Essentials using Apple Configurator for Mac or

Apple Configurator for iPhone, even if the devices weren’t purchased directly from Apple,

an Apple Authorised Reseller or an authorised network provider. When the administrator

sets up a device that has been manually enrolled, it behaves like any other device in one

of those services, with mandatory supervision and mobile device management (MDM)

enrolment. For devices that weren’t purchased directly, the user has a 30-day provisional

period to release the device from one of those services, supervision and MDM.

Organisations can also use Apple Configurator for Mac to activate iOS, iPadOS and tvOS

devices that have absolutely no internet connection by connecting them to a host Mac

with an internet connection while the devices are being set up. Administrators can restore,

activate and prepare devices with their necessary configuration including apps, profiles

and documents without ever needing to connect to either Wi-Fi or mobile networks. This

feature doesn’t allow an administrator to bypass any existing Activation Lock requirements

normally required during non-tethered activation.

196Apple Platform Security

Screen Time security

Screen Time is a built-in feature for seeing and managing how much time adults and

their children spend on apps, websites and more. There are two types of user: adults and

(managed) children.

Although Screen Time isn’t a new system security feature, it’s important to understand

how it protects the privacy and security of the data gathered and shared between devices.

Screen Time is available in iOS12 or later, iPadOS 13.1 or later, macOS 10.15 or later, and

some features of watchOS6 or later.

The table below describes the main features of Screen Time.

Feature Supported operating system

View usage data iOS

iPadOS

macOS

Enforce additional restrictions iOS

iPadOS

macOS

watchOS

Set web usage limits iOS

iPadOS

macOS

Set app limits iOS

iPadOS

macOS

watchOS

Configure Downtime iOS

iPadOS

macOS

watchOS

For users managing their own device usage, Screen Time controls and usage data can be

synced across devices associated with the same iCloud account using CloudKit end-to-

end encryption. This requires the user’s account to have two-factor authentication enabled

(syncing is on by default). Screen Time replaces the Restrictions feature found in previous

versions of iOS and iPadOS, and the Parental Controls feature found in previous versions of

macOS.

In iOS13 or later, iPadOS 13.1 or later, and macOS 10.15 or later, Screen Time users and

managed children automatically share their usage across devices if their iCloud account

has two-factor authentication enabled. When a user clears Safari history or deletes an app,

the corresponding usage data is removed from the device and all synced devices.

197Apple Platform Security

Parents and Screen Time

Parents can also use Screen Time in iOS, iPadOS and macOS devices to understand and

control their children’s use. If the parent is a family organiser (in iCloud Family Sharing),

they can view usage data and manage Screen Time settings for their children. Children are

informed when their parents turn on Screen Time, and they can monitor their own usage

as well. When parents turn on Screen Time for their children, the parents set a passcode

so their children can’t make changes. When they reach the age of majority (age will vary

depending on country or region), the children can turn this monitoring off.

Usage data and configuration settings are transferred between the parent’s and child’s

devices using the end-to-end encrypted AppleIDentity Service (IDS) protocol. Encrypted

data may be briefly stored on IDS servers until it’s read by the receiving device (for

example, as soon as the iPhone, iPad or iPodtouch is turned on, if it was off). This data

isn’t readable by Apple.

Screen Time analytics

If the user turns on Share iPhone & Watch Analytics, only the following anonymised data is

collected so that Apple can better understand how Screen Time is being used:

• Was Screen Time turned on during Setup Assistant or later in Settings

• Change in Category usage after creating a limit for it (within 90 days)

• Is Screen Time turned on

• Is Downtime enabled

• Number of times the “Ask for more” query was used

• Number of app limits

• Number of times users viewed usage in the Screen Time settings, per user type and per

view type (local, remote, widget)

• Number of times users ignore a limit, per user type

• Number of times users delete a limit, per user type

No specific app or web usage data is gathered by Apple. When a user sees a list of apps in

Screen Time usage information, the app icons are pulled directly from the AppStore, which

doesn’t retain any data from these requests.

198Apple Platform Security

Glossary

Address Space Layout Randomisation (ASLR) A technique employed by operating

systems to make the successful exploitation by a software bug much more difficult. By

ensuring memory addresses and offsets are unpredictable, exploit code can’t hard-code

these values.

AES (Advanced Encryption Standard) A popular global encryption standard used to

encrypt data to keep it private.

AES cryptographic engine A dedicated hardware component that implements AES.

AES-XTS A mode of AES defined in IEEE 1619-2007 meant to work for encrypting storage

media.

APFS (Apple File System) The default file system for iOS, iPadOS, tvOS, watchOS and

Mac computers using macOS 10.13 or later. APFS features strong encryption, space

sharing, snapshots, fast directory sizing and improved file system fundamentals.

Apple Business Manager A simple, web-based portal for IT administrators that provides

a fast, streamlined way for organisations to deploy Apple devices they have purchased

directly from Apple or from a participating Apple Authorised Reseller or network provider.

They can automatically enrol devices in their mobile device management (MDM) solution

without having to physically touch or prepare the devices before users get them.

AppleIDentity Service (IDS) Apple’s directory of iMessage public keys, APNs addresses,

and phone numbers and email addresses that are used to look up the keys and device

addresses.

Apple Push Notification service (APNs) A worldwide service provided by Apple that

delivers push notifications to Apple devices.

Apple School Manager A simple, web-based portal for IT administrators that provides

a fast, streamlined way for organisations to deploy Apple devices they have purchased

directly from Apple or from a participating Apple Authorised Reseller or network provider.

They can automatically enrol devices in their mobile device management (MDM) solution

without having to physically touch or prepare the devices before users get them.

Apple Security Bounty A reward given by Apple to researchers who report a vulnerability

that affects the latest shipping operating systems and, where relevant, the latest hardware.

Boot Camp A Mac utility that supports the installation of Microsoft Windows on supported

Mac computers.

199Apple Platform Security

Boot Progress Register (BPR) A set of system on chip (SoC) hardware flags that software

can use to track the boot modes the device has entered, such as Device Firmware Update

(DFU) mode and Recovery mode. After a Boot Progress Register flag is set, it can’t be

cleared. This allows later software to get a trusted indicator of the state of the system.

Boot ROM The very first code executed by a device’s processor when it first boots. As an

integral part of the processor, it can’t be altered by either Apple or an attacker.

CKRecord A dictionary of key-value pairs that contain data saved to or fetched from

CloudKit.

Data Protection A file and keychain protection mechanism for supported Apple devices.

Itcan also refer to the APIs that apps use to protect files and keychain items.

Data Vault A mechanism — enforced by the kernel — to protect against unauthorised

access to data regardless of whether the requesting app is itself sandboxed.

Device Firmware Upgrade (DFU) mode A mode in which a device’s Boot ROM code waits

to be recovered via USB. The screen is black when in DFU mode, but upon connecting to

a computer using iTunes or the Finder, the following prompt is presented: “iTunes (or the

Finder) has detected an (iPad, iPhone or iPodtouch) in Recovery mode. The user must

restore this (iPad, iPhone or iPodtouch) before it can be used with iTunes (or the Finder).”

direct memory access (DMA) A feature that allows hardware subsystems to access main

memory directly, bypassing the CPU.

Effaceable Storage A dedicated area of NAND storage, used to store cryptographic keys,

that can be addressed directly and wiped securely. While it doesn’t provide protection if an

attacker has physical possession of a device, keys held in Effaceable Storage can be used

as part of a key hierarchy to facilitate fast wipe and forward security.

Elliptic Curve Diffie-Hellman Exchange Ephemeral (ECDHE) A key exchange mechanism

based on elliptic curves. ECDHE allows two parties to agree on a secret key in a way

that prevents the key from being discovered by an eavesdropper watching the messages

between the two parties.

Elliptic Curve Digital Signature Algorithm (ECDSA) A digital signature algorithm based on

elliptic curve cryptography.

Enhanced Serial Peripheral Interface (eSPI) An all-in-one bus designed for synchronous

serial communication.

Exclusive Chip Identification (ECID) A 64-bit identifier that’s unique to the processor

in each iOS and iPadOS device. When a call is answered on one device, the ringing of

nearby iCloud-paired devices is terminated by briefly advertising through Bluetooth Low

Energy (BLE) 4.0. The advertising bytes are encrypted using the same method as Handoff

advertisements. Used as part of the personalisation process, it’s not considered a secret.

file system key The key that encrypts each file’s metadata, including its class key. This is

kept in Effaceable Storage to facilitate fast wipe rather than confidentiality.

Gatekeeper In macOS, a technology designed to help ensure that only trusted software

runs on a user’s Mac.

group ID (GID) Like the UID but common to every processor in a class.

hardware security module (HSM) A specialised tamper-resistant computer that

safeguards and manages digital keys.

200Apple Platform Security

HMAC A hash-based message authentication code based on a cryptographic hash function.

iBoot The stage 2 boot loader for all Apple devices. Code that loads XNU as part of the

secure boot chain. Depending on the system on chip (SoC) generation, iBoot may be

loaded by the Low Level Bootloader or directly by the Boot ROM.

Input/Output Memory Management Unit (IOMMU) An input/output memory management

unit. A subsystem in an integrated chip that controls access to address space from other

input/output devices and peripherals.

integrated circuit (IC) Also known as a microchip.

Joint Test Action Group (JTAG) A standard hardware debugging tool used by

programmers and circuit developers.

key wrapping Encrypting one key with another. iOS and iPadOS use NIST AES key

wrapping, in accordance with RFC 3394.

keybag A data structure used to store a collection of class keys. Each type (user, device,

system, backup, escrow or iCloud Backup) has the same format.

A header containing: Version (set to four in iOS12 or later), Type (system, backup, escrow

or iCloud Backup), Keybag UUID, an HMAC, if the keybag is signed, and the method used

for wrapping the class keys — tangling with the UID or PBKDF2, along with the salt and

iteration count.

A list of class keys: Key UUID, Class (which file or Keychain Data Protection class),

wrapping type (UID-derived key only; UID-derived key and passcode-derived key),

wrapped class key and a public key for asymmetric classes.

keychain The infrastructure and a set of APIs used by Apple operating systems and third-

party apps to store and retrieve passwords, keys and other sensitive credentials.

Low Level Bootloader (LLB) On Mac computers with a two-stage boot architecture, LLB

contains the code that’s invoked by the Boot ROM, and that in turn loads iBoot as part of

the secure boot chain.

media key Part of the encryption key hierarchy that helps provide for a secure and

instant wipe. In iOS, iPadOS, tvOS and watchOS, the media key wraps the metadata on the

data volume (and thus without it access to all per-file keys is impossible, rendering files

protected with Data Protection inaccessible). In macOS, the media key wraps the keying

material, all metadata and data on the FileVault protected volume. In either case, wipe of

the media key renders encrypted data inaccessible.

memory controller The subsystem in a system on chip that controls the interface between

the system on chip and its main memory.

mobile device management (MDM) A service that lets an administrator remotely manage

enrolled devices. After a device is enrolled, the administrator can use the MDM service

over the network to configure settings and perform other tasks on the device without user

interaction.

NAND Non-volatile flash memory.

nonce A unique one-off number used in various security protocols.

Passcode-derived key (PDK) The encryption key derived from the entangling of the user

password with the long-term SKP key and the UID of the Secure Enclave.

201Apple Platform Security

per-file key The key used by Data Protection to encrypt a file on the file system. The per-

file key is wrapped by a class key and is stored in the file’s metadata.

provisioning profile A property list (.plist file) signed by Apple that contains a set of

entities and entitlements allowing apps to be installed and tested on an iOS or iPadOS

device. A development provisioning profile lists the devices that a developer has chosen

for ad hoc distribution, and a distribution provisioning profile contains the app ID of an

enterprise-developed app.

Recovery mode A mode used to restore many Apple devices if it doesn’t recognise the

user’s device so the user can reinstall the operating system.

ridge flow angle mapping A mathematical representation of the direction and width of the

ridges extracted from a portion of a fingerprint.

Sealed Key Protection (SKP) A technology in Data Protection that protects, or seals,

encryption keys with measurements of system software and keys available only in hardware

(such as the UID of the Secure Enclave).

Secure Storage Component A chip designed with immutable RO code, a hardware random

number generator, cryptography engines and physical tamper detection. On supported

devices, the Secure Enclave is paired with a Secure Storage Component for anti-replay

nonce storage. To read and update nonces, the Secure Enclave and storage chip employ

a secure protocol that helps ensure exclusive access to the nonces. There are multiple

generations of this technology with differing security guarantees.

sepOS The Secure Enclave firmware, based on an Apple-customised version of the L4

microkernel.

software seed bits Dedicated bits in the Secure Enclave AES Engine that get appended to

the UID when generating keys from the UID. Each software seed bit has a corresponding

lock bit. The Secure Enclave Boot ROM and operating system can independently change

the value of each software seed bit as long as the corresponding lock bit hasn’t been set.

After the lock bit is set, neither the software seed bit nor the lock bit can be modified. The

software seed bits and their locks are reset when the Secure Enclave reboots.

SSD controller A hardware subsystem that manages the storage media (solid-state drive).

System Coprocessor Integrity Protection (SCIP) A mechanism Apple uses designed to

prevent modification of coprocessor firmware.

system on chip (SoC) An integrated circuit (IC) that incorporates multiple components

into a single chip. The Application Processor, the Secure Enclave and other coprocessors

are components of the SoC.

system software authorisation A process that combines cryptographic keys built

into hardware with an online service to check that only legitimate software from Apple,

appropriate to supported devices, is supplied and installed at upgrade time.

tangling The process by which a user’s passcode is turned into a cryptographic key and

strengthened with the device’s UID. This process helps ensure that a brute-force attack

must be performed on a given device, and thus is rate limited and can’t be performed in

parallel. The tangling algorithm is PBKDF2, which uses AES keyed with the device UID as

the pseudo-random function (PRF) for each iteration.

Unified Extensible Firmware Interface (UEFi) firmware A replacement technology for

BIOS to connect firmware to a computer’s operating system.

202Apple Platform Security

Uniform Resource Identifier (URI) A string of characters that identifies a web-based

resource.

unique ID (UID) A 256-bit AES key that’s burned into each processor at manufacture. It

can’t be read by firmware or software and it’s used only by the processor’s hardware AES

Engine. To obtain the actual key, an attacker would have to mount a highly sophisticated

and expensive physical attack against the processor’s silicon. The UID isn’t related to any

other identifier on the device including, but not limited to, the UDID.

xART An abbreviation for eXtended Anti-Replay Technology. A set of services that provide

encrypted, authenticated persistent storage for the Secure Enclave with anti-replay

capabilities based on the physical storage architecture. See Secure Storage Component.

XNU The kernel at the heart of the Apple operating systems. It’s assumed to be trusted,

and it enforces security measures such as code signing, sandboxing, entitlement checking

and Address Space Layout Randomisation (ASLR).

XProtect In macOS, an antivirus technology for the signature-based detection and

removal of malware.

203Apple Platform Security

Document revision history

Date Summary

December 2022 Topics added:

• Advanced Data Protection for i Cloud

Topics updated:

• i Cloud security overview

• i Cloud encryption

• Security of i Cloud Backup

• Account recovery contact security

• Legacy Contact security

204Apple Platform Security

Date Summary

May 2022 Updated for:

• iOS 15.4

• iPadOS 15.4

• macOS 12.3

• tvOS 15.4

• watchOS 8.5

Topics added:

• Paired recovery OS restrictions

• Local Operating System Version (love)

• Health sharing

• Account recovery contact security

• Legacy Contact security

• Tap to Pay on i Phone security

• Access using Apple Wallet

• Access credential types

• IDs in Apple Wallet

• Siri-enabled Home Kit accessories

Topics updated:

• Magic Keyboard with TouchID

• FaceID, TouchID, passcodes and passwords

• Facial matching security

• Express Cards with power reserve

• Boot modes for a Mac with Apple silicon

• Contents of a Local Policy file for a Mac with Apple silicon

• Signed system volume security in iOS, iPadOS and macOS

• System security for watchOS

• Apple Security Research Device

• Role of Apple File System

• Protecting app access to user data

• Intro to app security for macOS

• Protecting against malware in macOS

• i Cloud security overview

• Secure keychain syncing

• Secure i Cloud Keychain recovery

• Paying with cards using ApplePay

• Contactless passes in ApplePay

• Rendering cards unusable with ApplePay

• Apple Card application

• Apple Cash security

• Adding travel and e Money cards to Apple Wallet

• Secure Apple Messages for Business

• Face Time security

• Car key security in iOS

• Apple Configurator security

Topics removed:

• Home Kit accessories and i Cloud

205Apple Platform Security

Date Summary

May 2021 Updated for:

• iOS 14.5

• iPadOS 14.5

• macOS 11.3

• tvOS 14.5

• watchOS 7.4

Topics added:

• Magic Keyboard with TouchID.

• Secure intent and connections to the Secure Enclave.

• Auto Unlock and AppleWatch.

• Custom OS Image4 Manifest Hash (coih).

Topics edited:

• Added two new Express Mode transactions in Express

Cards with power reserve.

• Edited Secure Enclave feature summary.

• Software update content added to Secure Multi-Boot

(smb3).

• Additional content for Sealed Key Protection (SKP).

206Apple Platform Security

Date Summary

February 2021 Updated for:

• iOS 14.3

• iPadOS 14.3

• macOS 11.1

• tvOS 14.3

• watchOS 7.2

Topics added:

• Memory safe i Boot implementation

• Boot process for a Mac with Apple silicon

• Boot modes for a Mac with Apple silicon

• Startup Disk security policy control for a Mac with Apple

silicon

• Local Policy signing-key creation and management

• Contents of a Local Policy file for a Mac with Apple silicon

• Signed system volume security in iOS, iPadOS and macOS

• Apple Security Research Device

• Password Monitoring

• IPv6 security

• Car key security in iOS

Topics updated:

• Secure Enclave

• Hardware microphone disconnect

• recovery OS and diagnostics environments for an Intel-

based Mac

• Direct memory access protections for Mac computers

• Kernel extensions in macOS

• System Integrity Protection

• System security for watchOS

• Managing File Vault in macOS

• App access to saved passwords

• Password security recommendations

• Apple Cash security

• Secure Apple Messages for Business

• Wi-Fi privacy

• Activation Lock security

• Apple Configurator security

207Apple Platform Security

Date Summary

April 2020 Updated for:

• iOS 13.4

• iPadOS 13.4

• macOS 10.15.4

• tvOS 13.4

• watchOS 6.2

Updates:

• i Pad microphone disconnect added to Hardware

microphone disconnect.

• Data vaults added to Protecting app access to user data.

• Updates to Managing File Vault in macOS and Command-

line tools.

• Malware Removal Tool additions in Protecting against

malware in macOS.

• Updates to Shared i Pad security in iPadOS.

December 2019 Merged the iOS Security Guide, macOS Security Overview

and the Apple T2 Security Chip Overview

Updated for:

• iOS 13.3

• iPadOS 13.3

• macOS 10.15.2

• tvOS 13.3

• watchOS 6.1.1

Privacy Controls, Siri and Siri Suggestions, and Safari

Intelligent Tracking Prevention have been removed. See

https://www.apple.com/uk/privacy/ for the latest on those

features.

May 2019 Updated for iOS 12.3

• Support for TLS 1.3

• Revised description of Air Drop security

• DFU mode and Recovery mode

• Passcode requirements for accessory connections

November 2018 Updated for iOS 12.1

• Group Face Time

September 2018 Updated for iOS12 Secure Enclave

• OS Integrity Protection

• Express Card with power reserve

• DFU mode and Recovery mode

• Home Kit TV Remote accessories

• Contactless passes

• Student ID cards

• Siri Suggestions

• Shortcuts in Siri

• Shortcuts app

• User password management

• Screen Time

• Security Certifications and programmes

208Apple Platform Security

Date Summary

July 2018 Updated for iOS 11.4

• Biometric policies

• Home Kit

• ApplePay

• Business Chat

• Messages in i Cloud

• Apple Business Manager

December 2017 Updated for iOS 11.2

• ApplePay Cash

October 2017 Updated for iOS 11.1

• Security Certifications and programmes

• TouchID/FaceID

• Shared Notes

• Cloud Kit end-to-end encryption

• TLS update

• ApplePay, Paying with ApplePay on the web

• Siri Suggestions

• Shared i Pad

July 2017 Updated for iOS 10.3

• Secure Enclave

• File Data Protection

• Keybags

• Security Certifications and programmes

• Siri Kit

• Health Kit

• Network Security

• Bluetooth

• Shared i Pad

• Lost Mode

• Activation Lock

• Privacy Controls

March 2017 Updated for iOS10 System Security

• Data Protection classes

• Security Certifications and programmes

• Home Kit, Replay Kit, Siri Kit

• AppleWatch

• Wi-Fi, VPN

• Single sign-on

• ApplePay, Paying with ApplePay on the web

• Credit, debit and pre-paid card provisioning

• Safari Suggestions

209Apple Platform Security

Date Summary

May 2016 Updated for iOS 9.3

• Managed AppleID

• Two-factor authentication for AppleID

• Keybags

• Security Certifications

• Lost Mode, Activation Lock

• Secure Notes

• Apple School Manager

• Shared i Pad

September 2015 Updated for iOS9 AppleWatch Activation Lock

• Password policies

• TouchID API support

• Data Protection on A8 uses AES-XTS

• Keybags for unattended software update

• Certification updates

• Enterprise app trust model

• Data Protection for Safari bookmarks

• App Transport Security

• VPN specifications

• i Cloud Remote Access for Home Kit

• ApplePay Rewards cards, ApplePay card issuer’s app

• Spotlight on-device indexing

• iOS Pairing Model

• Apple Configurator 2

• Restrictions

210Apple Platform Security

Use of the “keyboard” Apple logo (Option-Shift-K) for commercial purposes without the prior written consent of

Apple may constitute trademark infringement and unfair competition in violation of federal and state laws.

Apple, the Apple logo, AirDrop, AirPlay, Apple Books, Apple Card, Apple Music, ApplePay, AppleTV, Apple Wallet,

AppleWatch, AppleScript, ARKit, Bonjour, Boot Camp, CarPlay, FaceID, FaceTime, FileVault, Finder, FireWire,

Handoff, HealthKit, HomeKit, HomePod, HomePod mini, iMac, iMac Pro, iMessage, iPad, iPadOS, iPad Air, iPad Pro,

iPhone, iPodtouch, iTunes, Keychain, Lightning, Mac, Mac Catalyst, Mac mini, Mac Pro, MacBook, MacBook Air,

MacBook Pro, macOS, Magic Keyboard, Objective-C, OS X, QuickType, Retina, Rosetta, Safari, Siri, Siri Remote,

SiriKit, Swift, Spotlight, TouchID, TrueDepth, tvOS, watchOS and Xcode are trademarks of AppleInc., registered in

the US and other countries and regions.

App Clips, Find My and Touch Bar are trademarks of AppleInc.

AppStore, AppleCare, CloudKit, iCloud, iCloud Drive, iCloud Keychain and iTunesStore are service marks of

AppleInc., registered in the US and other countries and regions.

Apple Messages for Business is a service mark of AppleInc.

Apple

One Apple Park Way

Cupertino, CA 95014

apple.com

IOS is a trademark or registered trademark of Cisco in the US and other countries and is used under licence.

The Bluetooth® word mark and logos are registered trademarks owned by Bluetooth SIG, Inc. and any use of such

marks by Apple is under licence.

Java is a registered trademark of Oracle and/or its affiliates.

UNIX® is a registered trademark of The Open Group.

Other product and company names mentioned herein may be trademarks of their respective companies.

Every effort has been made to ensure that the information in this manual is accurate. Apple is not responsible for

printing or clerical errors.

Some apps are not available in all areas. App availability is subject to change.

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